Estimating the cost of overweight vehicle travel on Arizona highways

Estimating the Cost of Overweight Vehicle Travel on Arizona Highways
Final Report 528
Prepared by: Sandy H. Straus ESRA Consulting CorporationTM rd 1650 South Dixie Highway, 3 Floor Boca Raton, Florida 33432 shs@esracorp.com John Semmens Arizona Department of Transportation th 206 S. 17 Avenue Phoenix, Arizona 85007
JANUARY 2006
Prepared for: Arizona Department of Transportation 206 South 17th Avenue Phoenix, Arizona 85007 in cooperation with U.S. Department of Transportation Federal Highway Administration
The contents of the report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The authors assume no liability for the use or misuse of any information, opinions, or conclusions contained in this report. The contents do not necessarily reflect the official views or policies of the Arizona Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Trade or manufacturers' names which may appear herein are cited only because they are considered essential to the objectives of the report. The U.S. Government and The State of Arizona do not endorse products or manufacturers.
Technical Report Documentation Page
1. Report No. 2. Government Accession No.
3. Recipient's Catalog No.
FHWA-AZ-06-528
4. Title and Subtitle 5. Report Date
January 2006
Estimating the Cost of Overweight Vehicle Travel on Arizona Highways
7. Authors
6. Performing Organization Code
8. Performing Organization Report No.
Sandy H. Straus and John Semmens
9. Performing Organization Name and Address 10. Work Unit No.
Sandy H. Straus ESRA Consulting Corporation 1650 South Dixie Highway, Third Floor Boca Raton, Florida 33432 (561) 361-0004 http://www.esracorp.com
11. Contract or Grant No.
SPR-PL-1-(59) 528
12. Sponsoring Agency Name and Address 13.Type of Report & Period Covered
ARIZONA DEPARTMENT OF TRANSPORTATION 206 S. 17TH AVENUE PHOENIX, ARIZONA 85007 Project Manager: John Semmens
15. Supplementary Notes
14. Sponsoring Agency Code
Prepared in cooperation with the U.S. Department of Transportation, Federal Highway Administration
16. Abstract
This study quantifies state highway damage on the basis of the impacts of overweight vehicles. Each year, millions of dollars of damage associated with life span, design, and maintenance of state highways and structures are attributed to vehicles that exceed state weight limits. Our best guess is that overweight vehicles impose somewhere between $12 million and $53 million per year in uncompensated damages to Arizona roadways. Arizona currently budgets about $5.8 million per year for mobile enforcement efforts aimed at, among other things, penalizing and deterring overweight vehicle operations. If a doubling of the mobile enforcement budget were 50% effective toward the objective of eliminating illegally overweight vehicles from Arizona roadways, the savings from avoided pavement damage would range from $6 million to $27 million per year. At the lower figure, the expansion of mobile enforcement would be a little better than a "break-even" proposition. The savings from avoided pavement damage would slightly exceed the cost of the program. Any safety gains from detecting and taking out-of-service vehicles with safety deficiencies would come on top of the pavement damage avoidance gains. At the higher figure, the expansion of mobile enforcement would have about a four- or five-toone benefit/cost ratio. That is, for every dollar invested in motor carrier enforcement efforts, there would be $4.50 in pavement damage avoided. Furthermore, we introduce a new truck lane design that may ultimately improve safety and optimize pavement usage in Arizona and other states.
17. Key Words 18. Distribution Statement 23. Registrant's Seal
Pavement damage, mobile enforcement, overweight vehicle, Arizona ports, pavement fatigue, US border, overweight truck, heavy truck, highway impacts, road damage, truck lanes, truck-only lanes, automation, highway cost estimate, pavement damage estimate, truckways, ESRA SPDE, weigh station, WIM
19. Security Classification 20. Security Classification
Document is available to the U.S. public through the National Technical Information Service, Springfield, Virginia 22161
21. No. of Pages 22. Price
Unclassified
Unclassified
81
SI* (MODERN METRIC) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS
Symbol When You Know Multiply By To Find Symbol Symbol
APPROXIMATE CONVERSIONS FROM SI UNITS
When You Know Multiply By To Find Symbol
LENGTH
in ft yd mi inches feet yards miles 25.4 0.305 0.914 1.61 millimeters meters meters kilometers mm m m km mm m m km millimeters meters meters kilometers
LENGTH
0.039 3.28 1.09 0.621 inches feet yards miles in ft yd mi
AREA
in ft2 yd2 ac mi2 fl oz gal ft3 yd3
2
AREA
square millimeters square meters square meters hectares square kilometers milliliters liters cubic meters cubic meters
3
square inches square feet square yards acres square miles fluid ounces gallons cubic feet cubic yards
645.2 0.093 0.836 0.405 2.59
mm m2 m2 ha km2 mL L m3 m3
2
mm m2 m2 ha km2 mL L m3 m3
2
Square millimeters Square meters Square meters hectares Square kilometers milliliters liters Cubic meters Cubic meters
0.0016 10.764 1.195 2.47 0.386
square inches square feet square yards acres square miles fluid ounces gallons cubic feet cubic yards
in2 ft2 yd2 ac mi2 fl oz gal ft3 yd3
VOLUME
29.57 3.785 0.028 0.765
VOLUME
0.034 0.264 35.315 1.308
NOTE: Volumes greater than 1000L shall be shown in m .
MASS
oz lb T ounces pounds short tons (2000lb) 28.35 0.454 0.907 grams kilograms megagrams (or "metric ton") Celsius temperature g kg mg (or "t")
?
MASS
g kg Mg grams kilograms megagrams (or "metric ton") Celsius temperature 0.035 2.205 1.102 ounces pounds short tons (2000lb) oz lb T
TEMPERATURE (exact)
?
TEMPERATURE (exact)
C
?
F
Fahrenheit temperature foot candles foot-Lamberts poundforce poundforce per square inch
5(F-32)/9 or (F-32)/1.8
C
1.8C + 32
Fahrenheit temperature foot-candles foot-Lamberts poundforce poundforce per square inch
?
F
ILLUMINATION
fc fl lbf lbf/in2 10.76 3.426 4.45 6.89 lux candela/m2 newtons kilopascals lx cd/m2 N kPa lx cd/m2 N kPa lux candela/m2 newtons kilopascals
ILLUMINATION
0.0929 0.2919 0.225 0.145 fc fl lbf lbf/in2
FORCE AND PRESSURE OR STRESS
FORCE AND PRESSURE OR STRESS
SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380
ESRA CONSULTING CORPORATION DISCLAIMER
Neither ESRA Consulting Corporation (ESRA), its affiliates, its associates, nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. References herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by ESRA or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of ESRA or any agency thereof. This report is for informational purposes only. Readers are encouraged to confirm the information contained herein with other sources. Reliance on any information in this report is solely at your own risk. ESRA Consulting Corporation is not responsible or liable for any direct, indirect, consequential, special, exemplary, or other damages arising from any use of any product, information, idea, or instruction contained in this report and all publications and presentations and/ or implementations therefrom. Notice is hereby provided that a patent application has been filed on one or more of the systems and methods described herein. Notice is hereby provided that ESRA may be involved in development and/ or marketing of products in the systems and/ or methods described herein. In the event that consideration is given to any component in the system described herein in which ESRA may have a marketing arrangement or other involvement, at the time of such consideration, full disclosure will be made.
I dedicate this report to the memory of my grandfather, Bernard, whose fascinations with the realms of transportation and automation were an inspiration to me. I always miss him. -SHS
TABLE OF CONTENTS
EXECUTIVE SUMMARY ............................................................................................................ 1 INTRODUCTION .......................................................................................................................... 3 I. FEDERAL TRUCK SIZE AND WEIGHT LIMITS ................................................................ 5 History............................................................................................................................................. 5 Current Federal Laws and Proposals .............................................................................................. 6 Highway Safety Implications.......................................................................................................... 6 The Feasibility of Truck-only Lanes............................................................................................... 6 II. MAGNITUDE OF OVERWEIGHT VEHICLE IMPACTS ................................................... 9 Pavement Types .............................................................................................................................. 9 Pavement Design ............................................................................................................................ 9 Pavement Maintenance and Life Span.......................................................................................... 10 Pavement Fatigue.......................................................................................................................... 10 Bridges and the Federal Bridge Formula ...................................................................................... 12 Pavement Costs............................................................................................................................. 14 The Significance of Fuel Taxes in Arizona and Other U.S. States............................................... 14 Pavement Cost Methods ............................................................................................................... 15 III. IDENTIFICATION OF OVERWEIGHT TRAFFIC ........................................................... 17 Manual and Automated Traffic Counting Techniques ................................................................. 17 Weigh-in-motion Sensors ............................................................................................................. 18 Traffic Data Collection Methods in Arizona ................................................................................ 19 IV. SURVEY OF TRANSPORTATION OFFICIALS AND/OR TRUCK ENFORCEMENT PERSONNEL FROM SEVERAL U.S. STATES AND CANADA .............. 23 Introduction................................................................................................................................... 23 Survey Responses ......................................................................................................................... 24 Conclusions................................................................................................................................... 45 V. THE CHALLENGE OF OVERWEIGHT VEHICLE ENFORCEMENT ............................. 47 VI. PAVEMENT DAMAGE ESTIMATION.............................................................................. 55 VII. CONCLUSIONS ................................................................................................................... 59 REFERENCES ............................................................................................................................. 61 APPENDIX A: ARIZONA FREIGHT FLOWS BY TRUCK AND ESTIMATED ANNUAL DAILY TRUCK TRAFFIC ........................................................................................ 67 APPENDIX B: TOP FIVE COMMODITIES SHIPPED TO, FROM, AND WITHIN ARIZONA..................................................................................................................................... 71 APPENDIX C: TRUCK CONFIGURATION, WEIGHT, AND FUEL ECONOMY................ 72
TABLES page Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 Table 12 Table 13 Table 14 Table 15 Table 16 Table 17 Table 18 Measured or estimated percentage of in-state travel comprised of vehicles exceeding legal limits (gross or axle or both) on weight Estimated cost of overweight vehicle damage Percentage of trucks on roads weighed at ports-of-entry Typical hours of operation for ports-of-entry Amount budgeted for mobile enforcement units on an annual basis Amount of mobile enforcement unit person-hours on an annual basis Quantity of vehicles weighed by mobile enforcement units/year Percentage of weighed vehicles exceeding legal limits through mobile enforcement units Average estimated number of pounds (lbs.) over the legal limit as reported by mobile enforcement units Some actions taken by state officials to reduce pavement damage Summaries of desired actions that are unfunded due to financial and other impediments The locations where most weight violations occur Time when most weight violations occur Classes and number of axles of vehicles that have the highest rate of in-state overweight violations Ratio of overweight permits you issue to overweight vehicle violations State Permits and Weight Violations, Fiscal Year 2003 Arizona & Neighboring State Permits & Weight Violations, FY 2003 Estimates of the Percentage of Overweight Vehicles FIGURES Page Figure 1 Figure 2 Typical hours of operation for ports-of-entry in selected states Amount of person-hours assigned to the duty of mobile enforcement units on a statewide annual basis in selected states 29 33 24 25 27 28 31 34 35 36 37 38 39 41 42 43 44 51 53 57
GLOSSARY OF ACRONYMS
AADT AASHTO ADOT ATPD ATRC AVC ESRA EVOC FHWA FBF GAO GVW IFTA IRP LCV LDOTD LTPP MCSAP MNDOT MVD NHTSA NN OAG SPDE TRB TRIP US USA USDOT VIUS WIM
Average Annual Daily Traffic American Association of State Highway and Transportation Officials Arizona Department of Transportation Arizona Transportation Planning Division Arizona Transportation Research Center Automatic Vehicle Classification ESRA Consulting Corporation Extra Vehicle Operating Costs Federal Highway Administration Federal Bridge Formula General Accounting Office Gross Vehicle Weight International Fuel Tax Agreement International Registration Plan Longer Combination Vehicle Louisiana Department of Transportation and Development Long Term Pavement Performance Motor Carrier Safety Assistance Program Minnesota Department of Transportation Motor Vehicle Division National Highway Traffic Safety Administration National Network State of Arizona Office of the Auditor General Straus Pavement Damage Estimation Transportation Research Board The Road Information Program United States United States of America United States Department of Transportation Vehicle Inventory and Use Survey (United States Census Bureau) Weigh-in-Motion
EXECUTIVE SUMMARY In order to quantify state highway damage, we seek to identify and evaluate the impacts of overweight vehicles on pavement. Since ancient times, pavements have played a vital role in trade and transportation throughout the world. Today, in the State of Arizona, the Arizona Department of Transportation (ADOT) and the ADOT Motor Vehicle Division (MVD) undertake the burden of law enforcement policies and activities associated with size and weight of vehicles on Arizona highways. Each year, overweight vehicles account for millions of dollars of damage connected with the life span, design, and maintenance of state highways and structures. Improvements are now needed on the roads and at all of the 22 Arizona ports in order to maintain the state's role as an economic powerhouse for freight activity in the years to come. Consequently, the results of this study may not only benefit the State of Arizona, but also other states and countries that face escalating costs associated with pavement fatigue and overweight vehicle enforcement challenges. Through survey techniques and a canvass of the literature, we identify the methods and expenditures that other states use for overweight vehicle issues and mobile enforcement units. We also introduce a unique truck lane design to aid mobile enforcement agents and minimize pavement damage. Arizona currently budgets about $5.8 million per year for mobile enforcement efforts aimed at, among other things, penalizing and deterring overweight vehicle operations in nearly 113,642 square miles of Arizona land area. The ADOT Simplified Highway Cost Allocation Model allows us to estimate that illegally overweight vehicles impose somewhere between $12 million and $53 million per year in uncompensated damages to Arizona roadways. The ADOT Simplified Highway Cost Allocation Model estimates that savings from avoided pavement damage would range from $6 million to $27 million per year if a doubling of the mobile enforcement budget were 50% effective toward the objective of eliminating illegally overweight vehicles from Arizona roadways. At the lower figure, the expansion of mobile enforcement would be a small improvement over a "break-even" proposition. The savings from avoided pavement damage would slightly exceed the cost of the program. Any safety gains from detecting and taking out-of-service vehicles with safety deficiencies would come on top of the pavement damage avoidance gains. At the higher figure, the expansion of mobile enforcement would have about a four- or five-toone benefit/cost ratio. That is, for every dollar invested in motor carrier enforcement efforts, there would be $4.50 in pavement damage avoided.
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INTRODUCTION Pavement fatigue is proportional to repetitive loadings. These loadings, attributed to traffic growth, generate pavement damage at earlier, faster, and costlier rates. The volume of truck traffic increases rapidly as the Interstate Highway System becomes available and popular. The overloaded truck, whether legal or illegal, contributes to premature pavement fatigue. These challenges lead to the need to develop new methods of pavement damage estimation and fatigue reduction techniques. The estimation of damage to state highway systems by overweight vehicles involves several variables. These may include the following, when available: ? ? ? ? ? ? ? Traffic counts for various segments, categorized by vehicle configuration. Weigh-in-motion (WIM), bridge and static scale measures for vehicles of various configurations. Highway spending related to overweight vehicle traffic. Commercial vehicle permits and/or registrations by weight class and configuration. Weight distance tax collections for years prior to the repeal of this tax. Weight citations recorded by state enforcement personnel. Diesel fuel consumption data1.
Overweight vehicle enforcement remains a problem in most U.S. states. As our survey demonstrates, the port and mobile enforcement crews are understaffed and/or under funded. Some lack qualifications or skills necessary to adequately detect and monitor overweight trucks. There are few ports equipped with cutting edge technology to adequately identify overweight truck violations. Ernzen reports that some ports are closed more hours than they are open.2 These circumstances lead to an inadequate enforcement of penalties for illegal overloads. Operators of illegally overloaded vehicles may also escape fines due to the failure of the judicial or administrative procedures dealing with detected violators. Billions of dollars are spent each year to replace and repair U.S. highways. Fines for illegal overloading are, therefore, not often correlated with the actual cost of pavement damage. Effectively monitoring and controlling truck weights are paramount to road preservation and minimization of pavement costs. Ultimately, the regulations that U.S. states uphold are intended to balance the economic benefits of commercial vehicle operations, particularly through large trucks. Nearly everything we own, eat, use, grow, or manufacture is carried by truck at least part of its
1 2
Straus, S. H. 2005. pending publication. Ernzen, J. M. 2005, Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
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journey. Trucks transport nearly three-fourths of the value and nearly two-thirds of the tonnage of all manufactured goods and raw materials shipped across the USA.3 Trucks are vital to the economy; illegal overweight trucks are not.
3
General Accounting Office . 2005. Large Truck Safety: Federal Enforcement Efforts Have Been Stronger Since 2000, but Oversight of State Grants Needs Improvement. GAO-06-156. Washington, D.C.
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I.
FEDERAL TRUCK SIZE AND WEIGHT LIMITS
History Federal Law regulates truck size and weight limits on interstate highways, national forests, national parks, and other federal lands. Some exceptions include those standards by "grandfather" right and provision for special permits.4 The Surface Transportation Assistance Act (STAA) of 1982 requires U.S. states to allow larger trucks on the National Network, which is comprised of the Interstate system plus the non-Interstate Federal-aid Primary System. All Federal and state laws, directly or indirectly, affect the quality and performance of pavement on our nation's highways. In 1941, Congress directed the Interstate Commerce Commission (ICC) to consider federal regulation of the sizes and weights of freight-carrying motor vehicles that were involved in interstate or international commerce. In 1956, the Federal Government initiated a program to regulate truck size and weight limits in order to improve federal investments in the Interstate Highway System. According to the DOT (2000): "A maximum gross weight limit of 73,280 pounds was established along with maximum weights of 18,000 pounds on single axles and 32,000 pounds on tandem axles. Maximum vehicle width was set at 96 inches.... States having greater weight or width limits... were allowed to retain those limits under a grandfather clause." 5 In 1975, a spike in fuel costs led the Congress to increase the allowable gross weight and axle weight limits. The U.S., through the STAA of 1982 (P.L. 97-424), adopted federal weight limits on Interstate Highways. Large trucks, such as 48-foot long semi-trailers, among others with prescribed minimum dimensions, were to be allowed on a National Network. A freeze on the expansion of operations on long combination vehicles followed in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) (P.L. 102-240). The Comprehensive Truck Size and Weight Study6 thoroughly examines issues associated with potential modifications of the current Federal truck size and weight (TS&W) limits. These include a foundation for cost and benefit analyses. In U.S. states, overweight permits are typically issued to routine overweight trucks. Fees are charged for these permits. These are intended to correspond to the additional infrastructure costs associated with the overweight vehicle. Sometimes these fees may cover only administrative costs of permit issuance. When moves often require special equipment and routing, permits may be issued for transports that involve heavier loads.
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 5 Ibid. 6 Ibid.
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Current Federal Laws and Proposals Federal law currently includes the following limits: ? ? ? 20,000 pounds for single axles on the Interstate System. 34,000 pounds for tandem axles on the Interstate System. Application of the Federal Bridge Formula for other axle groups up to the maximum of 80,000 pounds gross vehicle weight on the Interstate System.
Tandem axles are generally defined as two or more consecutive axles that are more than 40 inches but not more than 96 inches apart.7 From time to time, there have been proposals to increase the federal truck size and weight limits. Such proposals are controversial. Additional infrastructure costs, disruption of traffic flow, financial impacts on competing railroads, and potential adverse impacts on safety are all possible byproducts of increasing federal truck size and weight limits. As distance increases, rail appears as the preferred method of transportation. It is impossible to predict the extent to which U.S. states would allow larger and heavier vehicles to operate if no uniform nationwide criteria were in place. Yet, pavement quality and performance characteristics are ultimately shaped by truck size and weight policies. Trucks exert loads and vehicle forces on pavement. Therefore, pavement design must account for load distribution. Traffic volume, tire loads, axle configuration, vehicle speed, tire configuration, and load repetition, among others, all affect pavement. Highway Safety Implications Truck volume is a function of Federal truck size and weight restrictions. An increase in truck volume, especially among the very large and overweight motor carriers, compromises the safety of other motorists. Trucks contribute to congestion, traffic delays, and pavement fatigue. These increase the likelihood of a collision, injury, or fatality on the nation's highways. Overweight vehicles not only create infrastructure damage issues, but safety risks as well.8 The Feasibility of Truck-only Lanes Over the last 20 years, the volume of combination vehicles has doubled. By 2020, commercial truck travel may increase significantly and surpass all other vehicle travel in the U.S. Truck-only lanes are being proposed on some U.S. highways to accommodate the demand for large truck and commercial travel. These lanes, typically separate from high-speed traffic and other mixed-flow traffic, are allowed for the exclusive use of trucks. Few truck-only lanes exist in the USA. While trucks are restricted to certain
7
Arizona State Legislature. 2005. The Arizona Revised Statutes , 28-1100. Vehicles and loads; gross weight restrictions; exception. 46th Legislature, 2nd regular session. 8 Weight Tolerance Permits, Research Report 1323-2F, Texas Transportation Institute, Texas A&M University System and Texas Department of Transportation, 1994.
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lanes in most states, all vehicles are permitted use of the same lanes. According to a recent feasibility study conducted for the California Department of Transportation (CALTRANS), "....exclusive truck lanes were the most plausible for congested highways where three factors exist: (1) truck volumes exceed 30% of the vehicle mix, (2) peak hour volumes exceed 1,800 vehicles per lane-hour, and (3) off-peak volumes exceed 1,200 vehicles per lane-hour."9 The construction of truck-only lanes may ultimately improve safety and reduce traffic congestion. According to The Road Information Program (TRIP),10 National Highway Traffic Safety Administration (NHTSA) data from U.S. highways from 1998 to 2002 seem to support truck-only lane proposals. One-lane traffic fatalities involving large trucks account for about 0.5% of traffic fatality collisions in all lanes. Large truck traffic fatalities are highest in two lanes (75.5%) and four lanes (12.2%). Fatalities involving large trucks are greatest where the posted speed limit is 55 mph (37.8%) and 60 mph or higher (35%). The lower the posted speed limit, the fewer the number of large truck fatalities. In Arizona, an average of 100 people are killed in large-truck collisions each year. Samuel et al.11 present an interesting concept of "self-financing inter-city toll truckways," where heavy truck lanes are fitted with continuous concrete safety barrier(s) and "dedicated ingress and egress ramps and staging areas." A truckway is envisaged to exist "....either in its own right of way separate from any other roadway or located within the right of way of a limited-access highway, but which is completely separated from the mixed traffic lanes... and... fully grade separated and access controlled and may be one or two lanes in each direction." However, these custom-built and designed truck "freeways within-the-freeway" would involve considerable time and expense to construct. In-depth safety and economic analyses would be needed to prove such feasibility for the following reasons, among others: ? ? Jersey barriers or concrete traffic dividers are typically designed to minimize damage and reduce the likelihood of a car crossing into oncoming lanes in the event of a collision.12 Collisions that could occur in such truck "freeways within-the-freeway" could not only cost lives but additional collisions since heavy truck drivers would not have
California Department of Transportation (CALTRANS). 2004. "Truck-Only Lanes." CALTRANS: Traffic Operations Program, Office of Truck Services. May 24, 2004. < http://www.dot.ca.gov/hq/traffops/trucks/trucksize/fs-trucklanes.htm> 10 The Road Information Program. 2004. America's Rolling Warehouses: The impact of increased trucking on economic development, congestion, and traffic safety. http://www.tripnet.org/TruckingReport020904.PDF 11 Samuel, P., R. W. Poole, Jr., and J. Holguin-Veras. 2002. Toll Truckways: A New Path Toward Safer and More Efficient Freight Transportation. Policy Study 294. Los Angles, California: Reason Public Policy Institute. 12 McDevitt, C. 2000. "Basics of Concrete Barriers." In Public Roads. March/ April 2000. Volume 63. Number 5. Available from: <http://www.tfhrc.gov/pubrds/marapr00/concrete.htm>
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the option to easily switch to one or more traffic lanes in the event of an emergency or to avoid a bottleneck. Concrete barriers of various dimensions, specifically heights and thicknesses, as well as different mechanisms of reinforcement and shapes, may be required for safety purposes.
Of all the states, Arizona demonstrates the highest percentage increase (78%) in large truck travel over the 1998 to 2002 period. Large trucks pose a significant economic cost due to accelerated fatigue on the pavement. The pavement fatigue also increases vehicle wear that may impact vehicular performance and maintenance costs. Consequently, truck-only lanes might reduce the high costs associated with pavement maintenance and replacement. The accelerated pavement fatigue might then be limited to the truck-only lanes rather than all of the other lanes shared with all other motorists. The truck-only lanes would also aid roving enforcement agents in identification and tracking of suspect overweight vehicles. Truck-only lanes may not only prove to be a safe choice, but an economically feasible one as well. We, therefore, introduce truck-only lane designs13 that may be equipped with special sensors to allow mobile enforcement crews to remotely detect the presence of overweight trucks. These designs, as developed by ESRA Consulting Corporation TM, offer a significant and cost-effective improvement over others. Such lanes may be created within new or existing lanes to reduce costs. All trucks may drive on these lanes and therefore limit excess pavement damage to these lanes. Tolls may be an option based on the penalties assessed to illegally overweight truck drivers. Some states, however, may eventually add tolls to truck only lanes. Since these lanes are not fitted with any special sensors as we prescribe, all heavy truckers would be levied a toll. Therefore, our truckonly lane designs may ultimately improve safety, optimize pavement design, and strike a balance between the trucking industry, our government, and stakeholders. Since the safety implications of any new or existing lane construction requires consideration, further studies are now needed to aid in the development of truck-only lanes in Arizona and other states. However, their study, development, and implementation will not be possible without policy reforms by the state and federal government.
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For more information about these truck-only lane designs, please contact Sandy H. Straus, ESRA Consulting Corporation, 1650 South Dixie Highway, Third Floor, Boca Raton, Florida 33432, Telephone: 561-361-0004, e-mail: trucks@esracorp.com.
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II.
MAGNITUDE OF OVERWEIGHT VEHICLE IMPACTS
Pavement Types Flexible and rigid pavements are the two primary types of hard surfaced pavements. Flexible pavements are the most common. These cover 93% of all U.S. roads. Bituminous (asphalt) materials comprise flexible pavements. These are "flexible" because the traffic loads cause the total pavement structure to "bend" or "deflect." Flexible pavement design allows surface load stress to wane with depth. A layered system with progressively weaker materials generally provides adequate strength to resist the load stress. Pavements comprised of Portland cement concrete (PCC) have high stiffness and are therefore referred to as "rigid."14 The distribution of load over a subgrade, "the suspension system" of the pavement varies according to pavement type.15 However, pavement structure, mix design, and subgrade all influence the life and performance of the pavement. Pavement Design The design and analysis of pavement structures are primarily dependent upon traffic data. The American Association of State Highway and Transportation Officials (AASHTO) pavement damage equivalency equations and Highway Performance Monitoring System (HPMS) pavement functions govern the use and application of such data. Various procedures are used and identified in the 1993 AASHTO Guide for Design of Pavement Structures.16 For example, it is possible to convert a mixed traffic stream of different axle loads and axle configurations into a design traffic number. This can be achieved by converting each expected axle load into an equivalent number of 18 kipsingle-axle loads, known as equivalent single-axle loads (ESALs). The AASHTO damage concept, however, has some limitations. According to the Texas Transportation Institute, the AASHTO damage concept is based on a serviceability index.17 Some significant forms of damage such as bleeding or flushing of asphalt pavements are not directly integrated. Heavy loads on asphalt surfaces that have been designed for lighter loads may create this type of damage. A loss of skid resistance may result. This may be the byproduct of too much or too soft asphalt utilized for pavements supporting the heavy loads. A seal coat may be applied with an adequate quantity of asphalt to reduce heavy truck damage.
14
Hawaii Asphalt Pavement Industry. 2003. Available from: http://www.hawaiiasphalt.com/HAPI/modules/04_pavement_types/04_pavement_types.htm 15 United States Department of Transportation. 1998. Videotapes Explain the How and Why of Laboratory Test for Resilient Modulus. Focus, July/ August. 16 Guide for Design of Pavement Structures, Document Number: AASHTO GDPS-4, American Association of State and Highway Transportation Officials (Jan-1993). 17 Weight Tolerance Permits, Research Report 1323-2F, Texas Transportation Institute, Texas A&M University System and Texas Department of Transportation, 1994.
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Pavement Maintenance and Life Span Highway maintenance and condition are dependent on several variables, including but not limited to: climate, pavement layer thickness, pavement material quality, maintenance, roadbed soil properties, temperature, quantity and weights of axle loads and truck configurations on the pavement.18 Pavements are typically designed for an economic life of 20 years.19 Georgia's highways, for example, are engineered to sustain average traffic over a 20-year period.20 Bridges, however, are typically designed with an economic life of 75 years.21 These life spans pose a challenge for transportation infrastructure facilities to support a specified design load or number of load repetitions. The load characteristics of the anticipated traffic over the targeted useful design life of the structure are needed and not always available. Ideally, quality pavement is designed to last 30 years. However, fatigue may accelerate deterioration and result in earlier replacement. Since traffic volume is heaviest on the highways, and truck traffic continues to increase each year, pavement replacement may often be needed in less than ten years. Pavement fatigue remains the greatest threat to the quality and performance of every road. Pavement Fatigue Historically, highway infrastructure protection has been the primary consideration in determining truck size and weight limits.22 Weights and dimensions of trucks tend to influence the costs that highway agencies must bear to construct and maintain a highway system to serve present traffic and that anticipated in the future. Pavement deterioration accelerates with axle weight, the number of axle loadings, and the spacing within axle groups. The axle loads and spacing on trucks also affect the design and fatigue life of bridges. Truck dimensions influence roadway design -- truck width affects lane widths, trailer or load height affects bridge and other overhead clearances, and length affects intersection and curve design. Truck designs are determined by existing pavement and bridge strength and roadway geometry. Pavement failure is dependent on numerous variables, including but not limited to climate, environmental factors, materials, design, traffic, and usage. Since pavement damage increases with time, it is virtually impossible
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 19 Leidy, J. P., Clyde E. Lee and Robert Harrison. 1995. Measurement and Analysis of Traffic Loads Across the Texas-Mexico Border. Center for Transportation Research, University of Texas at Austin. For Texas Department of Transportation. 20 Performance Audit: Georgia Department of Transportation Permits and Enforcement Program, Performance Audits Operations, Department of Audits, State of Georgia, March 2000. 21 Jooste, F.J., E.G. Fernando, Victoria. Superheavy Load Move: Report on Route Assessment and Pavement Modeling, Cooperative Research Program Research Report 1335-1, Texas Transportation Institute, Texas A&M University System, October 1994. 22 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000.
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to pinpoint any specific illegally overweight truck to quantify its independent contributions to such damages. New construction costs, risks to public safety, and additional design requirements for the infrastructure are all byproducts of pavement fatigue.23 Cracking and/or joint-related problems create rigid pavement failure. This occurs when the tensile stress (from loading, temperature, etc.) exceeds the modulus of rupture.24 In theory, the concrete is expected to have an infinite life if the stress ratio is below 50%. In practice, this may be a challenge. When the stress ratio exceeds 50%, the number of load cycles to failure decreases rapidly. Axle groups, such as tandems or tridems, influence pavement load distribution. According to the Comprehensive Truck Size and Weight Study, these groups allow greater weights to be carried and result in the same or less pavement distress than that occasioned by a single axle at a lower weight.25 Pavement life and performance is also affected by the spread between two consecutive axles. The greater the spacing, the more each axle in a group acts as a single axle. Additionally, the steering axle of a truck can cause significant damage to pavement.26 Some observations show more total deflection under the steering axle than under the trailer axle. This may be due to horizontal offsets of steering tires versus dual trailer tires, tractor suspension system dynamics, and/or consistent static weight (tractor) loading on the steering axle, regardless of vehicle payload. According to the American Concrete Pavement Association, ESALs are defined as the "summation of equivalent 18,000-pound single axle loads used to combine mixed traffic to design traffic for the design period."27 ESALs are sometimes used to compare relative pavement impacts of various truck configurations with different numbers and types of axles.28 Increases in axle load correspond to increases in pavement fatigue. Traffic loadings greatly impact thinner pavements. Traffic loadings, coupled with environmental conditions, especially in places of variable climate, also accelerate the rate of pavement fatigue. Axles are the fixed bar or beam with bearings at its ends on which truck wheels revolve. The DOT reports that the net effect in axle spacing changes on
Preserving Highway Infrastructure Using Weigh-In-Motion (WIM). Dr. A.T. Bergan, Norm Lindgren, Dr. Curtis Berthelot , Bob Woytowich, University of Saskatchewan & International Road Dynamics Inc., November 1998. 24 Kilareski, W.P., "Heavy Vehicle Evaluation for Overload Permits," Rigid and Flexible Pavement Design and Analysis, Unbound Granular Materials, Tire Pressures, Backcalculation, and Design Methods, Transportation Research Record 1227, 1989. 25 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 26 Weight Tolerance Permits, Research Report 1323-2F, Texas Transportation Institute, Texas A&M University System and Texas Department of Transportation, 1994. 27 American Concrete Pavement Association. 2005. http://www.pavement.com/ 28 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000.
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pavement deterioration is complex and highly dependent on pavement structure.29 Tire characteristics vary according to materials, design, and manufacturer, among other variables. Consequently, the accelerated rutting of pavement is sometimes associated with tire characteristics. Wide-base single tires lack strong rut resistance and tend to cause 1.5 times more rutting than dual tires on the flexible pavements. In a laboratory, pavement impacts are observed by applying distresses and strains to different pavement samples. These pavement distresses are standardized to an 8,000pound axle equivalent through use of Load Equivalency Factors (LEF), which can differentiate between distresses, rather than an ESAL. Pavement distresses may include alligator (fatigue) cracking, bleeding, block cracking, corrugation and shoving, depression, joint reflection cracking, longitudinal cracking, patching, polished aggregate, potholes, raveling, rutting, slippage cracking, stripping, transverse (thermal) cracking, and water bleeding and pumping. The reader is referred to the website of Hawaii's Asphalt Pavement Industry in order to view photographs and information concerning each of these forms of pavement distress. 30 Aged asphalt pavements are susceptible to stiffness and brittleness due to an increase in viscosity. This leads to fatigue cracking. Therefore, rheological properties are very important to pavement design and performance. Rutting and bleeding may result from pavements that greatly deform and flow. In Georgia, for example, visible forms of pavement damage caused by overweight vehicles include, but are not limited to, rutting and load cracking.31 Load cracking happens when small pieces of pavement are dislodged from the surface of the road. Rutting occurs through permanent depressions in the pavement along the wheel path of traffic. Pothole development and shoulder damage are hazardous to passenger cars and school buses. Rut development contributes to severe hydroplaning, or wet pavement skidding. This poses a serious risk to drivers because traction is lost when water lifts a tire away from the road. Bridges and the Federal Bridge Formula Bridges were a different story. As urban and rural diverged and the population exploded, numerous bridges were built throughout the U.S. in the 1800s and 1900s. A bridge formula was needed to effectively reduce pavement and structural fatigue on bridges. In the 1940s, AASHTO recommended a bridge formula concept. It was not fully developed until 1962. The Federal-Aid Highway Amendments of 1974 required vehicles to comply with the Federal Bridge Formula (FBF).
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 30 Hawaii Asphalt Pavement Industry. 2003. Available from: http://www.hawaiiasphalt.com/HAPI/modules/04_pavement_types/04_pavement_types.htm 31 Performance Audit: Georgia Department of Transportation Permits and Enforcement Program, Performance Audits Operations, Department of Audits, State of Georgia, March 2000.
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The FBF is now used to preserve our nation's bridges and control vehicle weights. It is a function of the number of axles and axle spacing on a truck. It effectively calculates the maximum allowable weight on any group of axles. Some states, such as Arizona, use the FBF to determine the axle weights for overweight vehicles.32 The Federal Bridge Formula B33 is defined as: W = [LN/N-1 + 12N + 36] where: W = the maximum weight in pounds that can be carried by a group of two or more axles to the nearest 500 pounds L = the distance between the outer axles of the group N = the number of axles in the considered group The FBF is an approximation of the 5% and 30% overstress criteria.34 The National Bridge Inventory is used as a tool for the estimation of different scenario vehicles on a sample of bridges. While criteria vary from agency to agency, deficient bridges require replacement. Cracks develop in materials at points of high stress concentration. Steel bridges and pre-stressed concrete spans, if overloaded, are susceptible to fatigue. A doubling of stress creates an eight-fold increase in steel component damage. The repetitive applications of high stresses, particularly those produced by different motor vehicles, accelerate bridge fatigue. Therefore, the design stresses are far below stresses at which bridge failure occurs. The HS-20 and the H-15 are the most common bridge designs. These designs are based on one of two standard loadings. Heavy truck traffic on interstates and other highways call for the HS-20 bridge design. HS-20 designs typically replace H-15 designs. Lower functional class facilities, where older bridges are concerned, use the H-15 designs. Some states shore up bridges rather than replace them. Others opt for postings to prohibit use by the vehicles that would create the most damage. The cost of strengthening a bridge is a significant portion of the cost to replace the entire structure. Vehicle gross weight, the weight on various groups of axles, the distance between axles, and the type and length of bridge all influence the impact of truck and weight policies on bridges. Such policies significantly affect bridge impacts. Truck length, specifically
Arizona Department of Transportation, Motor Vehicle Division. 2005. Commercial Vehicle Enforcement. Available from: http://www.azdot.gov/mvd/faqs/scripts/faqs.asp?section=cp#4 33 United States Department of Transportation. 2004. Western Uniformity Scenario Analysis: A Regional Truck Size and Weight Scenario Requested by the Western Governors' Association. Washington, DC: United States Department of Transportation. 34 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000.
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wheelbase, greatly impacts bridge stress for long-span bridges.35 Further studies are now needed on the impacts of heavy trucks on fatigue and bridge deck deterioration. Pavement Costs Pavement costs vary from place to place and from time to time. Pavement costs are dependent on materials, thickness, quantity, and, of course, quality. Geographic and environmental conditions are also considered. The design life of pavements is dependent on these and other variables, including the volume of traffic, frequency of traffic, and the weight of the vehicles. These all take their toll on the life of pavements. Loads create compression and bending of pavements. These lead to rutting and cracking. Heavy axles cause greater and faster pavement fatigue than light axles. For example, a 24,000-pound truck axle consumes over 2,000 times as much pavement life as a 2,000-pound automobile axle.36 The Significance of Fuel Taxes in Arizona and Other U.S. States In order to defray the costs of pavement maintenance and replacement, state and federal taxes on fuels are assessed to drivers. Crude oil costs account for the largest cost of gasoline. Federal and state taxes are the second largest cost of gasoline. The tax on a gallon of diesel fuel is only slightly higher than the tax on gasoline used by most motor vehicles. Fuel taxes appear to shift the tax burden from heavier commercial vehicles to smaller passenger vehicles. Yet, heavy trucks create far greater pavement damage than these other motor vehicles. In fact, some engineers neglect car and light trucks with respect to pavement strength design.37 The fines, fees, and penalties that illegally overweight vehicle drivers face do not appear to be proportional to the pavement fatigue costs they cause. Fuel savings that may result from reduced vehicle travel that results from consolidating cargo into one overloaded trip are offset by highway deterioration and damaged pavement.38 In 1997, approximately $200 million of the revenues generated for the Arizona Highway User Revenue Fund derived from commercial motor carrier taxes. These taxes were based on vehicle miles traveled in Arizona and were monitored through these ports-ofentry.39
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 36 South Dakota Department of Transportation. 2002. SDOT Briefing: Truck Weights and Highways. 37 Corley-Lay, J. 2005. In "Troopers ticketing more heavy trucks," by Pat Stith. The News & Observer. August 17, 2005. <http://newsobserver.com/news/story/2728787p-9166402c.html> 38 Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987. 39 Norton, D. R, 1997. Performance Audit: Department of Transportation Motor Vehicle Division's Revenue Functions, Report to the Arizona Legislature, Report No. 97-4. Phoenix: State of Arizona Office of the Auditor General. http://www.auditorgen.state.az.us/Reports/State_Agencies/Agencies/Transportation,%20Department%20of /Performance/97-04/97-4.pdf
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In November 2004, the American Petroleum Institute reported that state and federal taxes on diesel fuel amounted to 52.4 cents per gallon plus 1 cent per gallon Underground Storage Tank tax in Arizona.40 This was only slightly higher than the U.S. average of 50.1 cents per gallon. An additional 9 cents per gallon on diesel fuel was also assessed to Arizona vehicles with a gross weight of 26,000 pounds or over. In September 2005, regular grade gasoline was offered at the same price as diesel fuel in some cities in Arizona and across the USA. This was primarily due to a disruption in fuel supplies attributed to Hurricane Katrina.41 This led many to speculate that any major natural or unnatural disaster could spark significant fuel shortages and price inflations. Between 1950 and 2002, the amount of gasoline and diesel usage increased dramatically in Arizona. Consumption increases were 1287% for gasoline and 6550% for diesel. In Arizona, large truck travel was projected to increase by 78% between 2003 and 2010. This is one of the highest rates of increase in the country, following Utah (82%) and Nevada (85%).42 The rise in diesel fuel usage corresponds to a jump in truck traffic and, therefore, higher costs than ever for pavement maintenance and replacement.43 Further spikes in diesel fuel costs may also contribute to an increase in illegally overweight motor carriers as truckers seek to economize and haul heavier cargo. The Congress may be pressured to increase the allowable gross weight and axle weight limits, as it was in 1975 due to the jump in fuel costs. Such legislation would contribute to accelerated pavement fatigue and expenses. Pavement Cost Methods Marginal cost and incremental cost are two economic cost methods used for highway damage cost analysis. Tolliver defines the long run cycle of a highway as the entire time of existence from initial construction to abandonment.44 The addition of one more ESAL to a highway section leads to marginal cost impact analysis. This corresponds to the additional consumption of highway capacity. Incremental costs account for relatively large traffic increases as opposed to a single ESAL analysis.45 Yet, as discussed, highway
American Petroleum Institute. 2004. Policy Analysis and Statistics. "Nationwide and State-by-State Motor Fuel Taxes," November 2004. Available from: http://apiec.api.org/filelibrary/Gas%20tax%20November%202004%20Final.pdf 41 ESRA Consulting Corporation. 2005. Internal report. 42 The Road Information Program. 2004. America's Rolling Warehouses: The impact of increased trucking on economic development, congestion, and traffic safety. http://www.tripnet.org/TruckingReport020904.PDF 43 Arizona Transportation Planning Division. 2003. 2002 Arizona Transportation Factbook: Transportation Relevant Statistical Information. Phoenix: Arizona Department of Transportation. http://tpd.az.gov/reports/pdf/2002factbook.pdf 44 Tolliver, Denver. Highway Impact Assessment. Westport, Connecticut: Quorum Books, 1994. 45 Eriksen, Ken, Kenneth L. Casavant, Impact of Increased International Trade (NAFTA) on Washington Highways, Part II: Highway Impact by Corridor, EWITS Research Report Number 25, Washington State University and US Department of Agriculture, November 1998.
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damage costs fluctuate so these models may not offer the practicality that pavement damage analyses require. In actuality, it is very difficult to assess highway damage costs due to data requirements that most ports and mobile enforcement units lack. Pavement damage is dependent upon many variables and complexities. No equation or model we know of accounts for each of these variables. The few estimates that are available are either outdated or specific to one locality.
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III. IDENTIFICATION OF OVERWEIGHT TRAFFIC Manual and Automated Traffic Counting Techniques Traffic volume is estimated by counting the number of vehicles that pass a point along a highway or street during a specified time period. Traffic detectors automate the counting of passing vehicles. The most common traffic measuring equipment is a pneumatic road tube. Tubes are placed across the road perpendicular to the traffic stream. A counting device is triggered through changes in tube pressure as axles pass over the tube. However, these devices only record axle passage. The data must be converted to vehicles and vehicle classes according to preset axle-spacing parameters. Therefore, some degree of error is anticipated. 46 In contrast, induction loop detectors, which are embedded in the pavement, record the passage of actual vehicles rather than axles. Other sensing equipment includes sonar and radar detectors. However, these devices are generally used for real-time traffic flow monitoring. They are not typically calibrated for traffic counting and classification. According to the ADOT HPMS Data Team, 2002, "raw" traffic counts are conducted with rubber tubes stretched across the road. These must be adjusted to compensate for over-counting by multi-axle vehicles. Traffic classification allows for the development of axle correction factors, which are applied to any raw, tube-based counts. Traffic counts obtained by magnetic induction loops that are permanently imbedded beneath a roadway surface eliminate the need for axle factoring. The presence of a vehicle via a magnetic field is detected by electronic traffic counters connected to "loops." Similarly, wires that are installed in the street at signalized intersections activate signal changes. Such techniques reduce the likelihood of an over-count of vehicles with a lot of axles, such as multi-trailer ("18-wheeler") trucks.47 Tubes or loops are generally used to obtain raw traffic counts. These require seasonal adjustments to compensate for monthly and daily fluctuations of vehicular traffic. Such adjustments are done prior to the quote or publication of any traffic volume information. This adjusting procedure provides a traffic volume that best approximates the use of a given highway section for a typical 24-hour day of the year. Automatic traffic recorders (ATR), a network of continuous traffic recorder stations, produce seasonal adjustment factors. The ADOT Data Section operates 69 ATR stations statewide, which monitor vehicular traffic twenty-four hours each day of the year. These ATR stations are "polled" daily via telemetry and computer software to report the previous day's travel activity. Traffic data polled from ATRs are stored and processed in both monthly and annual
46
GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 47 Average Annual Daily Traffic, Arizona Department of Transportation, Transportation Planning Division, Data Team. http://tpd.azdot.gov/datateam/aadtinfo.php
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cycles, which are subsequently applied to raw counts taken on all highway segments that are assigned to a particular set of ATR stations. Once the field crews obtain and report the raw traffic counts, the data are downloaded and stored in a computer. These are later processed and converted to average annual daily traffic volumes (AADT). While it is important to gauge the volume of truck traffic, it is equally imperative to know the weights of the trucks for enforcement and safety purposes. Traditionally, the static scales are in widespread use. However, with the advent of WIM sensors, this technology is gradually supplementing, if not replacing, a lot of scales at ports across the USA. In Arizona, the use of WIM stems from a feasibility study that installed and assessed slow speed Weigh-In-Motion (SWIM) equipment for enforcement applications.48 Weigh-in-motion Sensors WIM devices are commonly used as an alternative to static weigh stations. WIM allows for the effective monitoring of gross vehicle and axle weight monitoring as trucks drive over a sensor. The WIM captures and records the data without requiring the trucks to stop. It provides real-time and accurate counts and gauges compliance with state and federal laws. The WIM scale takes an instantaneous reading of a fluctuating or oscillating force. Since WIM recorders convert signals from the sensors into load values, there is a potential for WIM measurement errors. Dynamic loading errors appear to be dependent on a number of factors including acceleration, braking, road conditions, vehicle speed, and vehicle type. 49 Therefore, the recorders must be recalibrated frequently.50 WIM Systems are classified according to Type I, II, III, or IV according to application through American Society for Testing and Materials (ASTM) Designation E 1318-94.51 These vary according to user requirements and performance. Different data gathering capabilities, speed ranges, and uses define the four different WIM systems.52 There are three types of sensors commonly used in WIM Systems. These include the bending-plate sensors, piezoelectric sensors, and single load cell scale. The bending48
Castle Rock Consultants. 1989. Port of Entry Weigh-In-Motion Feasibility Study. FHWA-AZ89-702. Phoenix, Arizona: Arizona Department of Transportation. 49 Oregon Department of Transportation Research Unit, Policy and Research Section, Transportation Development Branch, Oregon Department of Transportation. 1998. Port-of-Entry Advanced Sorting System (PASS) Operational Test. FHWA-OR-RD-99-15. 50 GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 51 American Society for Testing and Materials. 1994. Standard Specification for Highway Weigh-inMotion (WIM) Systems with User Requirements and Test Method. ASTM Committee E-17 on VehiclePavement Systems. ASTM Designation E 1318-94. 52 McCall, B. and W. C. Vodrazka. 1997. State's Successful Practices Weigh-In-Motion Handbook. Washington, DC: Department of Transportation Federal Highway Administration.
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plate sensors consist of steel plates embedded in concrete pavement. The plate deflects in an amount proportional to the load when a vehicle passes over the plate. The amount of deflection is transmitted to a data recorder. The load is computed. Bending plate sensors are believed to be more durable and accurate than piezoelectric sensors. Piezoelectric sensors, contrastingly, consist of a casing containing a piezoelectric material. This generates an electrical charge when subjected to mechanical stress. The vehicle load creates a charge that is proportional to the stress it produces. Piezoelectric sensors are an economical alternative to bending-plate sensors and can be moved from location to location. The Single Load Cell Scale constitutes a single hydraulic load cell installed at the center of each platform to measure the force applied to the scale. When properly installed and calibrated, Single Load Cell WIM systems are expected to provide gross vehicle weights that are within 6% of the actual vehicle weight for 95% of the trucks measured.53 Road conditions, road geometry, and vehicle condition impact WIM system performance. Vehicle dynamics also affect the accuracy level of the WIM systems. Accuracy is therefore lower than that for a static scale used for enforcement weighing. No absolute accuracy for a WIM scale exists. Therefore, any WIM accuracy is always quoted as a percentage accuracy with a confidence level. The confidence level is generally set at either 68% or 95%. ASTM accuracy uses the 95% level, which means that we can be 95% confident that the actual weight is within the measured WIM stated range.54 At weigh stations, Automatic Vehicle Identification devices may check registration and safety data. Since axle or truck weights are not identifiable by this technology, Strathman and Theisen also suggest the use of WIM.55 Automatic Vehicle Identification devices, used in combination with WIM technology, may offer cost-effective enforcement options. Traffic Data Collection Methods in Arizona A recent study conducted by the ADOT documents discrepancies in data collection and equipment.56 ADOT collects and maintains traffic volumes for all highways at specific collection sites. Some sites record traffic volumes continuously throughout the year, but most sites are only counted for 48 hours once a year. The results of the collection effort are used to compile or compute AADT values for every section of the state highway system.
Weigh In Motion Technology - Economics and Performance. Rob Bushman, Andrew J. Pratt. Presented at NATMEC '98, Charlotte, North Carolina, 1998. 54 Ibid. 55 Strathman, J. G. and G. Theisen. 2002. Weight Enforcement and Evasion: Oregon Case Study. FHWAOR-DF-02-12. Salem, Oregon: Oregon Department of Transportation. 56 GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation.
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AADT is the average 24-hour traffic volume at a given location over a full 365-day year. Therefore, the AADT at a given site is calculated by dividing the total number of vehicles passing a site in a year by 365. About 70 collection sites are equipped with ATRs, which record traffic continuously throughout the year. For sites at which a 48-hour count is used, the site AADT is estimated by factoring the 48-hour count by seasonal, monthly, and day-of-week adjustments.57 ADOT uses several types of technology for automated traffic counting. Automatic traffic recorders (usually inductive loop detectors) are primarily used at the continuous monitoring sites, and pneumatic tube detectors for short-term counts. The ATR data are used to determine seasonal adjustments to short-term counts. Some of the ATR sites also record vehicle classification and weight. Specific sites are established for the collection of vehicle classification data. These sections are assumed to represent all highway sections within a specified area. Data collection at these sites is shared between the Long Term Pavement Performance (LTPP) program at the Arizona Transportation Research Center, and the Transportation Planning Data Team.58 ADOT performs manual vehicle classification counts at a few sites. Manual counts are performed over 6-hour intervals. In other locations, traffic counting devices are used to conduct 48-hour counts. These devices convert axle observations and measurements to vehicle classes, based on assumptions programmed into the recording devices. Finally, several sites are equipped with continuous automatic vehicle classification (AVC) devices that function in the same manner as the ATR equipment. All AVC sites use axle sensors and induction loops for vehicle detection and classification.59 The MVD, the ADOT Materials Group, and the Arizona Transportation Research Center (ATRC) all collect vehicle weight data for Arizona highways. MVD collects truck weights for enforcement purposes, while the Materials Group and the ATRC collect vehicle weight measurements for pavement management and research. The MVD uses static scales at port-of-entry (POE) locations statewide to measure gross vehicle weight and axle loads. While these scales have the benefit of a high degree of accuracy, static scales are insufficient for the measurement of a large volume of traffic. POE stations do not have the technical resources for truck weight data collection and storage, as the enforcement operations only require weight data for an inspection in progress. Weight records are recorded only at stations with WIM sensors, and these data are only maintained on the WIM recorder for a 24-hour period. 60 ADOT is currently in the midst of implementing the Data Collection Project. The Data Collection Project entails collecting vehicle counts and weights at selected MVD sites on a 24 hours-a-day, 7-days-a-week basis. ADOT is also striving to include all data
57
GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 58 Ibid. 59 Ibid. 60 Ibid.
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collection devices into a combined database in order to provide a better picture of where and when the heavy trucks are running. These data and information will be used to deploy our mobile operations at those locations identified as routes that overweight vehicles most frequently use. This should also help reduce circumvention of fixed POE sites. The Data Team and ATRC use WIM sensors to record weight measurements for vehicles traveling at highway speeds. ADOT uses two types of WIM sensors for these applications: bending plates and piezoelectric cables. However, these sensors are not always operational. ADOT Transportation Technology Group staff report that approximately 50% of the Freeway Monitoring System traffic sensors function at a given time. According to the Data Team, about 90% of the ATRs used to collect data for the HPMS fail at least once per year. A recent study shows that, on a given day, only 74% of the ATRs (55 out of 74) transmitted any data.61 Not every port in Arizona uses WIM technology. WIM sensors may only be present in one of two lanes of traffic. The lack of WIM sensors means that many overweight vehicles will not be detected. This will result in uncompensated costs due to pavement damage induced by overweight vehicles that are not weighed, monitored, or cited for infractions.62 On the other hand, according to interviews with ADOT staff, the WIM sensors are not particularly effective for capturing vehicle weight data. Certain bending-plate installations are only operational for a 3-month period before being rendered unusable due to excessive traffic loading. Hence there is a dire need for not only improved technologies, but also a calculation that will account for the data collection discrepancies that exist within agencies, highways, and elsewhere.
GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 62 Ernzen, J. M. 2005, J. M. 2005. Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
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IV. SURVEY OF TRANSPORTATION OFFICIALS AND/OR TRUCK ENFORCEMENT PERSONNEL FROM SEVERAL U.S. STATES AND CANADA Introduction ESRA developed a survey to ascertain the state-of-the-practice of current mobile enforcement activities across the nation. Questionnaires were faxed, e-mailed, and/or queried by telephone to the directors and public safety officials of all 50 U.S. states and the ten provinces and three territories of Canada from January to April 2005. Some officials were telephoned for follow-up interviews. Responses were received from 25 states: Alabama, Indiana, Oregon, Alaska, Louisiana, Tennessee, Arizona, Maryland, Texas, Arkansas, Missouri, Utah, California, Montana, Vermont, Colorado, Nebraska, Washington, and Delaware, North Dakota, Wisconsin. Georgia, Ohio, Illinois, Oklahoma, Two responses were obtained from Canada: The Province of Nova Scotia and The Territory of Nunavut. Not all respondents from the U.S. and Canada answered all the questions on the survey. The majority of data requested was either undetermined or unavailable due to funding or staffing issues. Many respondents indicated that tasks were divided among different agencies. The information for South Dakota was acquired from "SDOT Briefing: Truck Weights and Highways." Additional information on Arizona Ports of Entry was obtained through "Arizona Ports of Entry: Arizona Department of Transportation JLBC/OSPB Joint SPAR Report," 2000 Strategic Program Area Review. It was then reported that there were "....13 ports, 9 mobile stations, 142 officers, and a Phoenix Central Permits office which only issues permits" under the auspices of ADOT-MVD.63 By 2005, Ernzen reported that there were 21 fixed ports of entry in the State, six of which were located on the Arizona-Mexico border.64 Our aim was to review and learn about the policies and practices of other agencies and bureaus in order to quantify and, ultimately, reduce pavement damage associated with overweight vehicles. Clearly, there is a dire need for improved mobile enforcement units, equipment, and data collection "across the board," in all U.S. states. Arizona is a state that merits further
Arizona Department of Transportation. 1999. Arizona Ports of Entry: Arizona Department of Transportation JLBC/OSPB Joint SPAR Report, 2000 Strategic Program Area Review (available from: http://www.azleg.state.az.us/jlbc/ports.pdf) 64 Ernzen, J. M. 2005, J. M. 2005. Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
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attention due to its border with Mexico. As our survey demonstrates, geography, economy, industry, and climate appear to influence the number of violations by overweight vehicles in most U.S. states. For example, in Georgia, there are numerous overweight vehicles associated with the wood industry. In Indiana, these overweight vehicles may be linked to quarries and construction activities. Overweight vehicles create costly damage to roads and structures. Some violators know the schedule of the mobile enforcement units and strategically violate the weight limits after hours of operation. Other violations occur during operating hours in daylight. Survey Responses Question #1 1. What is the measured or estimated percentage of travel in your state that is comprised of vehicles exceeding legal limits (gross or axle or both) on weight? __________ (If there is a report, memo, or other document, can you send us a copy?) Table 1. Measured or estimated percentage of in-state travel comprised of vehicles exceeding legal limits (gross or axle or both) on weight STATE Arizona Delaware* Indiana* Louisiana Montana Nebraska Oregon South Dakota Utah Washington Wisconsin Alaska, Colorado, Georgia, Illinois, Maryland, Missouri, North Dakota, Ohio, Oklahoma, Tennessee, Vermont * varies by route PERCENTAGE 30 ~5 ? 20 <2; 3-5 2 6.9 <0.5 10 0.5 <10 <5 7 Unknown
Only 11 states provided estimates of the percentage of trucks that were operating in excess of legal weight limits. Arizona's estimate of 30% is by far the highest. Most of the other states perceive the overweight vehicle traffic to amount to less than 10% of the trucks operating on their roadways.
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Question #2 2. Have you estimated a cost in terms of damage to pavements, structures, or safety due to these overweight vehicles?
Yes No
If "yes" what are these costs? ___$________________________________________ (If there is a report, memo, or other documents, can you send us a copy?) Table 2. Estimated cost of overweight vehicle damage STATE Indiana Maryland Montana South Dakota Vermont Alaska, Arizona, Arkansas, Colorado, Delaware, Georgia, Illinois, Louisiana, Missouri, Nebraska, North Dakota, Ohio, Oklahoma, Oregon, Tennessee, Utah, Washington, Wisconsin ESTIMATED COST OF DAMAGE Rural- $1 million per lane per mile Urban- over $1 million per mile due to property costs. $36 million per year due to overweight dump trucks $700,000 more than $1.1 million in six county bridge replacements in the last 2 years. > $1,000,000 Not estimated
Only four states have attempted to estimate the damage caused by overweight vehicles. The quality of these estimates is undetermined. Indiana's seems implausibly high. For that state Interstate Highway system alone, the cost would be in the $3.5 billion range. This is $2 billion more than Indiana spends per year for ALL state highway expenses. At the other extreme, Montana's estimate seems implausibly low given the state's $500 million annual expenditure on state highways. Maryland's estimate is focused on dump trucks. This partial information cannot be extrapolated to other classes of vehicle. South Dakota's data is limited to the impacts on six specific bridges. Vermont's estimate of over a million dollars in damage is a safe statement, but too imprecise to be of much use. The paucity of good information on this issue is truly disappointing. The importance of having good information is emphasized by ADOT's Intermodal Transportation Division projection that a 10% jump in overweight vehicles could cause a
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$20 million annual increase in costs associated with road repair and maintenance.65 Roads designed for life spans of 20 years may fall short of that without adequate weight enforcement. Question #3 3. Have you done any studies of overweight vehicles in response to proposals to change the weight limits? If so, can you summarize the outcome of that/those studies? (If there is a report, memo, or other document, can you send us a copy?) Only eight states professed to have conducted studies of overweight vehicles: Colorado, Georgia, Indiana, Louisiana, Missouri, Montana, North Dakota, and Washington. None of these studies specifically linked weight to pavement damage in any scientifically quantified way. Some technical reports are either unpublished or based on studies performed by other U.S. states. For example, Colorado, like Minnesota, considers increasing weight limits during the winter months. However, the various frost depths in Colorado reveal that increasing weight loads during frozen periods is not possible. In order to increase weights on state roads in Georgia, bills are introduced each year when legislature is in session. In Missouri, studies exist on the impacts of increased legal weights on bridges, as proposed by legislation. In Washington, requests are routinely received "...to increase axle loads for `specialty' vehicles (i.e., cement trucks, refuse haulers, emergency response equipment, etc.)." The Washington Department of Transportation uses their layered elastic program (Everstress) to analyze such pavements and to estimate the damages caused by axle load increases through increases in required asphalt thicknesses. These studies, performed by the HQ Materials Pavement Division and the Commercial Vehicle Services branch of the Washington Department of Transportation indicate that the state is successful in its enforcement of axle weight and weight per inch of tire requirements. Indiana intends to enforce existing weight limit laws and utilize virtual weigh stations rather than modify weight limits. In South Dakota, illegal haulers who violate weight limits are pursued through enforcement and prosecution methods. Other states, such as Texas, do not currently have initiatives to change the weight limits, reported at Gross: 80,000 lbs.; Tandem Axle: 34,000 lbs.; Single Axle: 20,000 lbs.
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Arizona Ports of Entry: Arizona Department of Transportation JLBC/OSPB Joint SPAR Report, 2000 Strategic Program Area Review (available from: http://www.azleg.state.az.us/jlbc/ports.pdf
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Question #4 4. What percentage of the total of trucks on your roads is weighed at your ports-of-entry? ___________________________________________________ Table 3. Percentage of trucks on roads weighed at ports-of-entry STATE Alaska Arizona Georgia Illinois Indiana Louisiana Montana Ohio Oklahoma Oregon Utah Wisconsin Arkansas, California, Colorado, Missouri, Tennessee, Vermont Delaware, Maryland, North Dakota, Texas PERCENTAGE 5.2% 98% 70% 40% 100% weighed on WIM 15% 17.86% 3% 5 to 10% 35%-55% 35-40% 68.7% unknown Not applicable (No state port-of-entry)
Given that ports-of-entry deal with interstate traffic and are not always open, the lower percentages reported here seem more plausible. The higher percentage estimates may represent the ratio of vehicles stopped at the POEs that actually are weighed. Some may not be weighed for efficiency reasons. For example, a flatbed truck without a load is obviously not overweight and may not need to be weighed. Some may not be weighed due to the queue length. If the queue stretches beyond the ramp's storage capacity it would constitute a safety hazard. Trucks arriving when there is no space on the ramp may be waived through the POE without stopping. Some states, such as Oregon, report the use of PrePass. PrePass is an automatic vehicle identification (AVI) system that allows participating transponder equipped commercial vehicles to bypass designated weigh stations, port-of-entry facilities, and agricultural interdiction facilities. Cleared vehicles may proceed at highway speed, eliminating the need to stop.66 While seemingly useful, this system seems to have some limitations. PrePass may check the safety credentials of the driver yet not weigh the vehicle. Vermont performs weight enforcement activities through use of Platform, portable wheel
66
http://www.prepass.com/aboutprepass.htm
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weigh loaders, Semi-portable scales, and WIMs. In Missouri, fixed sites, HSWIMSPrePass, portable scales, and RampWIMs are used to weigh millions of vehicles per year. At the Texas-Mexico border, there are eight ports-of-entry. All trucks entering Texas from Mexico pass over weigh-in-motion scales at these ports-of-entry. Vehicles that fail the weigh-in-motion are weighed on a static scale. Question #5 5. Please indicate typical hours of operation for your ports-of-entry: ________hours Table 4. Typical hours of operation for ports-of-entry STATE Alaska Arizona HOURS 24-hour shifts "Depends on POE (Port of Entry). A large Interstate POE is supposed to operate 7 days a week, 24 hours a day. A smaller secondary POE might be 16 hours 5 to 7 days a week according to traffic and/or staffing. Some are 8 hours five days a week. International POEs hours of operation are determined by Customs agency." 24-hour shifts 24-hour shifts 24-hour shifts 2- 8 hour shifts 16-hour shifts 8-hour shifts 24-hour shifts Not Applicable 18- 24 hours 8-24 hours Not Applicable 8-hour shifts 8-hour shifts 18- 24 hours 24-hour shifts 18-hour shifts 20- 24 hours 12-hour shifts 16-hour shifts
Arkansas California Delaware Georgia Illinois Indiana Louisiana Maryland Missouri Montana North Dakota Ohio Oklahoma Oregon Tennessee Texas Utah Vermont Wisconsin
While several states maintain round-the-clock operation of their POEs, most do not. Drivers of overweight vehicles aware of the closing times of POEs not operating 24 hours a day may time their trips to ensure bypassing a closed POE.
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For example, the eight ports-of-entry in Texas "...operate at varying hours from 6AM to Midnight on weekdays." These ports are managed on the same schedule as the U.S. Customs & Border Protection ports-of-entry. In Oklahoma, "Hours of operation are selectively expanded in response to a need for increased enforcement...from keeping weigh stations open longer hours, varying the hours at specific weigh stations, or double shifts for all stations in January to check registration. The Corporation Commission is facing the same budgetary constraints as ODOT. All of the agencies involved in weight enforcement are working together to maximize available resources."
Not applicable 10%
Varies according to Port-of-entry 13%
2- 8 hour shifts 5%
24-ho ur shifts 28%
8-ho ur shifts 14%
12-ho ur shifts 5%
18- 24 shifts 10%
16-ho ur shifts 10% 18-ho ur shifts 5%
Figure 1. Typical hours of operation for ports-of-entry in selected states
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According to Vermont, "Sixty percent of DMV enforcement activity is spent on state initiatives i.e. size, weight, IFTA (International Fuel Tax Agreement), IRP (International Registration Plan), dyed fuel etc. and the other forty percent is MCSAP (Motor Carrier Safety Assistance Program) enforcement activities in which weight enforcement can be part of a MCSAP inspection. Most officers, based on national statistical violation trends, work Monday ? Friday between the hours of 0600-1800 hours. Inspectors may work outside of that time frame but the bulk of our activity is during the listed days and time." In Arizona, the hours of operation vary from port-of-entry to port-of-entry. "A large Interstate POE is supposed to operate 7 days a week, 24 hours a day. A smaller secondary POE might be 16 hours 5 to 7 days a week according to traffic and/or staffing. Some are 8 hours five days a week. International POES hours of operation are determined by the Customs agency." Unsurprisingly, the respondents with limited hours of ports-of-entry operation expressed interest in extending hours of operation. However, budget and staffing issues prevented such activities. Nowhere was this more evident than in Arizona, where, since 1998, truck traffic increased significantly while the hours of operation at Arizona ports were cut by 39%.67
67
Ernzen, J. M. 2005, J. M. 2005. Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
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Question #6 6. For your mobile enforcement units on a statewide annual basis, typically: a. How much is budgeted for this effort? _________________________________ b. How many person-hours are assigned to this duty? _______________________ c. How many vehicles are weighed? ____________________________________ d. What percentage of the weighed vehicles exceeds the legal limits? __________ e. How many pounds (lbs.) over the legal limit do overweight vehicles average? __________________________________________________________ Table 5. Amount budgeted for mobile enforcement units on an annual basis STATE Alaska Arizona Arkansas California Colorado Delaware Georgia Illinois Louisiana Maryland Missouri Montana North Dakota Oklahoma Texas Utah Vermont Indiana, Oregon, Tennessee, Wisconsin MOBILE ENFORCEMENT BUDGET $600,000 "$5.8 million total personnel costs, facilities" $12,213,614 "$88,922,000 for commercial vehicle inspection and enforcement." $1.6 million $675,000 $18,973,729 $400,000 $2,227,072 "cost absorbed in overall budget of approximately $12 million per year" "$1,527,812 (vehicles, fuel, maintenance and salaries)" "$712,340 expended" $90,000 ~ $2,500,000 "State Funding: $27,008,917; Federal Funding: $24,170,994 (POE Operations)" $500,000- $700,000 $748,690 unknown
The amount budgeted for mobile enforcement units on a statewide annual basis vary from state to state. Since some figures reached into the tens of millions of dollars, it was assumed that these respondents indicated the overall budget amounts rather than their mobile enforcement unit budgets. Such mobile enforcement unit costs were typically absorbed into the overall budgets. For example, as shown in Table 5, in California, the amounts reported were $88,922,000 (for commercial vehicle inspection and
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enforcement); and in Texas, $51,179,911 (for state and federal funding). Of this Texas budget, $24,170,994 was earmarked for ports-of-entries. This study determined that, among all respondents who reported specifically their mobile enforcement unit budgets, the average amount budgeted for mobile enforcement units in these states was approximately $3.7 million. In Arizona, the mobile enforcement budget was estimated at $5.8 million for total personnel costs and facilities. The budget in North Dakota was lowest at $90,000. In Tennessee, a merger between the Commercial Vehicles Enforcement unit and the Highway Patrol recently occurred through the Department of Safety. It was reported that troopers were assigned to either road patrol or fixed inspection stations. The troopers were not assigned to a set number of hours per day of mobile weight enforcement. A lack of calibrated and certified portable wheel weighers resulted in very few trucks being weighed. Therefore, no budgets or statistics we requested were available at the time this questionnaire was issued. Approximately $600,000 is budgeted yearly in Nova Scotia for mobile enforcement units. This is about the same amount budgeted in Alaska and slightly less than the amount budgeted in Delaware. In Figure 2, the amount of person-hours assigned to the duty of mobile enforcement units on a statewide annual basis in responding states is presented. This amount is dependent on location, need, funding, and staffing operations. Approximately 23% of the U.S. respondents report 2,000- 9,999 hours annually. There are 21,500 person-hours assigned to mobile enforcement unit duties in Nova Scotia.
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Amount of person-hours assigned:
100,000- 450,000 hours 10%
60,000- 99,999 hours 10%
Unknown 28%
26,000- 55,999 hours 10%
10,000- 25,999 hours 19%
2,000- 9,999 hours 23%
Figure 2. Amount of person-hours assigned to the duty of mobile enforcement units on a statewide annual basis in selected states
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Table 6. Amount of mobile enforcement unit person-hours on an annual basis STATE Alaska Arkansas California Colorado Delaware Illinois Louisiana Maryland Missouri Montana North Dakota Oklahoma Oregon Texas Utah Vermont Arizona, Georgia, Ohio, Tennessee, Wisconsin MOBILE ENFORCEMENT PERSON-HOURS* 21,450 3,224 413,504 54,000 8,320 249,600 62,400 40,000 139,776 25,000 5,000 79,000 2,000 2,080 18,720 16,000 Unknown
*lower numbers of person-hours may be per person rather than total numbers of mobile enforcement unit person-hours.
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Table 7. Quantity of vehicles weighed by mobile enforcement units/year STATE California Alaska Arizona Arkansas Colorado Delaware Georgia Illinois Maryland Missouri Montana North Dakota Oregon Texas Utah Vermont Wisconsin Indiana, Oklahoma, Tennessee QUANTITY OF VEHICLES WEIGHED 16,226,790 (includes portable scales: 458; Fixed scales: 11,61,670; WIM 4,264,662 ) 3,495 4,575,085 4,532 51,698 "The annual target is 650 vehicles for portable weigh pads." 10,444,582 ~45,000 ~25,000 3,666 6,358 1,100 ~7,500 881,948 (includes Fixed Scales: 292,053; Semi-Portable Scales: 36,605; Portable Scales: 15,225; WIM: 538,065) 5,400,000 23,732 1,090 unknown
Table 7 shows that Wisconsin (1,090) and North Dakota (1,100) weigh the fewest vehicles. Georgia (10,444,582), Utah (5,400,000), and Arizona (4,575,085) weigh the most vehicles each year. Portable scales account for weighing 650 vehicles in Delaware and 458 vehicles in California. In Texas, a total of 881,948 vehicles are weighed through use of fixed scales (292,053), semi-portable scales (36,605), portable scales (15,225), and WIM (538,065). There are 4,600 vehicles weighed each year in Nova Scotia, Canada. The large variation may be due to errors. Some respondents may have included total quantity of vehicles weighed by both static and mobile enforcement crews. California officials, for example, provide a complete breakdown of the quantities and techniques of vehicles weighed.
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Table 8. Percentage of weighed vehicles exceeding legal limits through mobile enforcement units STATE Alaska Arizona Arkansas Colorado Illinois Louisiana Maryland Montana North Dakota Oregon Texas Utah Wisconsin Delaware, Georgia, Indiana, Missouri, Ohio, Oklahoma, Tennessee, Vermont WEIGHED VEHICLES EXCEEDING LEGAL LIMITS 0.23% 0.53% 0.29% 12% ~27.1% ~25% 1.4% 10.33% 50% ~5% 3 to 4% 2-3% "nearly 100%" unknown
The overweight violation percentages range from tiny to nearly 100%. It seems likely that high percentages reflect targeted enforcement. That is, only those vehicles suspected of being overweight are pulled aside by these states' mobile enforcement units. For example, the North Dakota Highway Patrol weighs only 1,100 vehicles per year on a very small annual budget of less than $90,000. However, the mobile enforcement units report that the overweight vehicles are, on average, 3,000 to 8,000 lbs. overweight.
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Table 9. Average estimated number of pounds (lbs.) over the legal limit as reported by mobile enforcement units STATE Utah Wisconsin Illinois Montana Alaska North Dakota Oregon Texas Arizona, Arkansas. Colorado, Delaware, Indiana, Maryland, Missouri, Ohio, Tennessee, Vermont AVERAGE NUMBER OF POUNDS (LBS.) THAT WEIGHED VEHICLES EXCEED LEGAL LIMITS 10,000 6,500 "6,000 over" 4,500 4,000 3,000-8,000 "For calendar year 2004 the overall average violation was 2,278 pounds." "Data is not available; but usually exceeds the weight allowance by a minimum of 1,000 lbs. before enforcement action is initiated." unknown
While most respondents were unable to provide us with this data, such data as are available may be useful to know in order to improve mobile enforcement activities and reduce pavement damage from overweight vehicles. The Iqaluit office of Nunavut, Canada is equipped with a portable weigh-scale that was used to monitor a situation, several years ago, where overloaded rock-trucks were in frequent operation. Now, the Government of Nunavut reports, the scale is rarely needed and used. In Nova Scotia, Canada, mobile weighers are increased in order to reduce the damage caused by overweight vehicles. Question #7 7. What other actions (if any) does your state take to try to reduce the damage caused by overweight vehicles? (If there is a report, memo, or other documents, can you send us a copy?) ____________________________________________
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Table 10. Some actions taken by state officials to reduce pavement damage
STATE Alaska Arkansas California Colorado Georgia Illinois Indiana Louisiana Maryland Missouri ACTIONS "....increased roadside inspections and portable scale weighings..." "The development of virtual weigh stations on secondary bypasses. This study will not end until June 2006. No statistics have been gathered at this time." "Weigh more vehicles, construct more port of entry inspection facilities, relocate and upgrade certain platform scales at inspection facilities." "Vehicle/load combinations in excess of 100 tons are sent to CDOT's Staff Bridge for further analysis and bridge impact." "Have mobile teams off the main interstates and have semi-portable weighing operations at wood mills." "Keep weigh stations open as much as possible." "...educational initiatives to educate the public; judicial outreach program to educate attorneys, prosecutors in representing the state..." "Many overweight loads are routed by our Oversize/Overweight Permit Office personnel to reduce their impact on roads and bridges." "Issue oversize/ overweight permits." "We use the routine overweight permitting process for weights between 80,000# and 152,000#. For these loads and configurations we compare the proposed move to the capacity of the bridges using "envelope" vehicles. For weights greater than 152,000# and non-routine configurations (i.e., superloads) we do an individual bridge analysis (load rating) for all structures crossed along the route by the proposed vehicle. By having these processes, we ensure that the structures are safe to cross along with helping to protect our bridges from sustaining damage during the move. Also, we will load post bridges that do not have the capacity to carry legal loads." "....Planning & Research Division is investigating semi-active vibration absorber technology with regard to bridges. Oklahoma is also working toward automating Oversize/Overweight permitting..." "We computerize scale data and track company weight violation rates. If a company with above average violation rates is based in or has a terminal in Oregon, we contact the company and set up training classes to educate and gain voluntary compliance." stringent penalties and enforcement "We attempt to deploy what certified portable wheel weighers that we do have in traditionally known areas of violations." "Overweight penalties were recently increased for repeat violators." "Departmental action, civil; occasional spring load restrictions." "Enact spring weight restriction period. Suspend or limit use of overweight permits. Post sections of poor roads." Not specified
Oklahoma Oregon
South Dakota Tennessee Texas Utah Wisconsin Arizona, Delaware, Montana, North Dakota, Ohio, Vermont
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The actions taken to reduce overweight vehicle damage are presented in Table 10. Georgia maintains mobile teams off the main interstates and has semi-portable weighing operations at wood mills. Indiana offers a judicial outreach program to educate attorneys in representing the state. Tennessee targets traditionally known areas of violations with the deployment of certified portable wheel weighers. South Dakota issues stringent penalties and enforcement. Louisiana routes overweight loads through its Oversize/overweight Permit Office personnel to reduce their impact on roads and bridges. Texas increases overweight penalties for repeat violators. Oklahoma investigates semiactive vibration absorber technology with respect to bridges. Oklahoma also plans to automate OS/OW permitting. Colorado sends vehicle/load combinations in excess of 100 tons "...to CDOT's Staff Bridge for further analysis and bridge impact." Oregon computerizes scale data to track company weight violation rates. In an effort to gain compliance, companies within Oregon that demonstrate "above average violation rates" are educated through training classes. Question #8 8. What are the actions you would like to take, but are prevented from taking due to financial or other impediments? ________________________________________ Table 11. Summaries of desired actions that are unfunded due to financial and other impediments DESIRED ACTIONS* Additional personnel and equipment Attract and retain qualified enforcement employees through an improved pay plan. Charge more for overweight permits; equivalent to damage done to pavement. Extend hours of weigh station operations. Extend spring weight restriction period. Increase fines/ civil penalties/ weight operations. Increase statewide activities Installation of virtual weigh stations. Installation of Weigh in Motion and/ or portable weigh stations at additional statewide locations. lengthen scale decks and repave more scale ramps re-certify and deploy our portable wheel weighers Transmit WIM data through wireless technology Unspecified * Some states provided more than one response. STATES Indiana, Louisiana, Maryland, Utah Montana Wisconsin Illinois, North Dakota Wisconsin Colorado, Georgia, Wisconsin Alaska, Georgia Arkansas Arkansas, Montana, Tennessee Oregon Tennessee Vermont Arizona, Delaware, Ohio
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In Table 11, the respondents reveal a wish-list of unfunded yet desirable actions. For example, Vermont currently uses WIM stations for screening. However, inspectors "....must physically open the box and boot up the work station monitor in order to observe real time vehicle weights." Therefore, an update of the VDOT WIM stations is necessary for inspectors to monitor roadside traffic from laptops that use wireless technology. According to an official in Oregon: "All of the 91 Oregon DOT scales use 16' decks. We are seeing more and more trailers today with 4 and greater axle groups with air suspension and 18 ? 20 foot spreads. .... when we attempt to weigh the axle groups by splitting them and weighing in two groups, the air suspensions move air and change the weights. We are lengthening scale decks at seven of our interstate scales that frequently weigh these vehicles. By being able to weigh the entire group at once, the weight will be absolutely accurate. As the infrastructure ages, the costs to repave or maintain scale ramps are high. While, in the ideal, I wish had more money to repave more scale ramps, but we are holding our own." Some states, such as Louisiana, note the need for improved technologies at weigh station bypass routes and the construction of new weigh stations at key locations. Some logistical obstacles seem to exist with mobile weight enforcement operations now under the auspices of the State Police rather than the Department of Transportation. In Nova Scotia, Canada, like most U.S. states, there exists a need for additional vehicles and personnel.
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Question #9 9. Where do most of your weight violations occur? Please check all that apply: Vehicles traveling interstate Vehicles traveling intrastate Vehicles traveling across the US/Mexico Border (if applicable) Vehicles traveling across the US/Canada Border (if applicable) Table 12. The locations where most weight violations occur LOCATION OF MOST WEIGHT VIOLATIONS Intrastate Interstate and Intrastate Interstate STATE Alaska, Arizona, Colorado. North Dakota, Ohio, Oklahoma, Vermont, Utah, Wisconsin Arkansas, Illinois, Maryland, Montana Georgia, Louisiana, Missouri, Tennessee California, Delaware Indiana Oregon
Unknown "Borman, I-80/ I-94" "We do not track the interstate versus intrastate status of loads cited for weight violations. Most of the violations we discover are on the interstate highways because that is where we weigh the most trucks. However, you cannot jump to the conclusion they are interstate loads. The better question is where is the highest violation rates? They are at the scales on the lesser traveled highways where trucks operators are not used to seeing more truck weighing effort." Interstate, Intrastate, and U.S./ Texas Mexico Border
While these responses are not conclusive, the relatively higher preponderance of intrastate being seen as the more likely traffic to run overweight would indicate that POEs would be ineffectual in stemming violations by these vehicles. This would tend to argue for either more internal weigh stations or a more active mobile enforcement effort (or both).
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Question # 10 10. When do most of your weight violations occur? _______________________ Table 13. Time when most weight violations occur TIME 6 AM ? 8 PM 6 AM ?12 midnight After hours Between 12-4 P.M. Daylight and early evening Daytime During the construction and harvest seasons No specific time or pattern Spring and fall When weigh stations are open Unknown STATE Colorado Texas Indiana, Oklahoma Montana Louisiana Delaware, Georgia, Ohio, Oregon, Vermont North Dakota Alaska, Illinois, North Dakota, Utah Wisconsin Georgia Arizona, Arkansas, California, Maryland, Missouri, Tennessee
There is not enough consistency in the responses to suggest any useful timing of countermeasures. Anecdotal evidence suggests that knowing violators are likely to try to avoid getting weighed. This would support an "after hours" perception of when most violators are operating. Daytime responses probably reflect the fact that citations are only written when enforcement officers are working, which are during daylight hours. For example, survey respondents in Oklahoma replied: "We do know that truckers frequently gather at rest areas ahead of a weigh station and wait for the station to close for the day (generally around 2 to 3 pm)."
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Question #11 11. Which classes of vehicle have the highest rate of overweight violations in your state? (Please specify number of axles.) _________________________ Table 14. Classes and number of axles of vehicles that have the highest rate of instate overweight violations STATE Alaska Arizona Arkansas Colorado Delaware Illinois Indiana Louisiana Maryland Montana North Dakota Oklahoma Oregon Texas Utah Vermont Wisconsin California, Georgia, Missouri, Ohio, Tennessee * depends on geographic area CLASS AND/OR TYPE OF VEHICLES Class 9 (3S3s__single trailer) 18-wheelers Class 9 Class 7 Class 9 Semi-tractor trailer Class 9 "Type 6" Class 9 "truck and pup" "...rock haulers,... grain haulers, and oil field equipment trucks. ..." "tandem overload" "combinations" and "single vehicles" "....typically refuse trucks, dump trucks, LCVs, hauling coal and rock." Combination vehicles, "double bottoms" unknown NUMBER OF AXLES 5 5 5 5 5 5 4 or 5*
3* 3 and 5 6 and above 5 and 6
Class 9 (5-axle) vehicles seem to be the most frequently cited overweight vehicles. Officials in Arizona, Arkansas, Delaware, Illinois, Indiana, and Louisiana report that 5axle motor vehicles yield the highest rate of in-state overweight violations. Maryland and Texas officials also identify the 5-axle motor vehicles. Three-axle trucks and six-axle tractor-trailer combinations account for the highest rate of overweight vehicles in Nova Scotia, Canada.
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Question #12 12. What is the ratio of overweight permits you issue to overweight vehicle violations?___________________________________________________ Table 15. Ratio of overweight permits you issue to overweight vehicle violations STATE Alaska Arizona Arkansas California Colorado Delaware Georgia Illinois Indiana Louisiana Maryland Missouri Montana North Dakota Ohio Oklahoma Oregon RATIO 2.18:1 unspecified 11.78% (40,987 overweight permits: 3,478 violations notices being issued.) 3.95% 1.36%; Overweight permits issued ? 15,764, Overweight violations ? 11,561 unknown 60% 2.5% 2% Overweight Permits ? 84,862; Overweight Fines ? 54,116; Approx. 1.6 to 1 unknown "3.22. It is unknown how many violations were written on vehicles not permitted." 5.94% unknown unknown Approximately 0.65 "For calendar year 2004, we documented 24,728 overweight violations. During the same period we issued approximately 154,000 annual and single trip permits. The ratio of violations to permits is 1:6.2." unknown 77.8%; 43,820 permits: 5,663 overweight citations 42.8%; 26,600 to 622 unknown
Tennessee Utah Vermont Wisconsin
It is difficult to interpret these responses. For many the math is clearly incorrect. Most respondents compare permits to citations written. Of course, it seems likely that the number of violations vastly exceeds the number of citations written. In reality "unknown" is probably the only accurate answer in this list of responses.
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Conclusions If anything is clear from these survey results, it is the fact that hard data on overweight vehicles is sorely lacking. The range of estimates for the percentage of vehicles that are overweight ranges from less than 1/2% to a high of 30%. Some perceive a serious problem. Others see no significant problem. No state was able to produce a credible estimate of the amount of damage that might be attributed to overweight vehicles. There is no coherent vision of weight enforcement that permeates the thinking of practitioners. Some enforcement personnel imagine they are weighing nearly every truck. The reality is that only a minority of trucks is likely weighed. Ports-of-entry are not consistently manned and operated. When POEs are closed in the evenings or on weekends the highways are open for overweight violators. Mobile enforcement would appear a potentially useful measure in detecting and deterring overweight vehicles. Yet, the commitment to this strategy varies greatly. Some states' mobile units weigh millions of vehicles yearly. Others weigh just a few thousand. The damage done by overweight vehicles is insidious rather than immediately overt. Roads are long-lived assets. The increment of damage from one overweight vehicle goes unseen. Consequently, it is difficult to stimulate an effective response to counter the damage. Nonetheless, greater attention to the issue is warranted. At the very least, we need better data.
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V. THE CHALLENGE OF OVERWEIGHT VEHICLE ENFORCEMENT While U.S. federal guidelines remain in place, the definition, measurement procedures, assessment, and damage quantification of overweight vehicles vary from state to state. A review of the literature supplements the ESRA survey and demonstrates that the challenges of overweight vehicle enforcement and identification are historic, complex, widespread, and costly. In 1979, the General Accounting Office (GAO) suggested that approximately 15% of all loaded trucks were overweight with respect to allowable axle loads or GVW. The GAO also cited a lack of uniformity among the U.S. states with respect to enforcement, penalties, and permit administration.68 The Federal Highway Administration (FHWA) identified various ways through which truck weight violations were adjudicated.69 The FHWA found that the judicial system did not adequately address the severe social costs associated with overweight vehicle violations. There appeared to be a lack of understanding associated with the implications of such violations. Illegally overloaded trucks were then estimated to cost taxpayers $160 to $670 million per year for pavement costs at the national level. Meanwhile, the illegally operating carriers reaped the benefits of overloading the taxpayer's highways by gaining an unfair advantage over their honest competition through greater profit margins. They also avoided the responsibility of covering the pavement damages they created. Nevertheless, law-abiding carriers and the associations representing truckers supported the stringent enforcement of truck weight laws to eliminate the unfair advantage of illegally operating carriers. By 1987, a published questionnaire distributed to state enforcement agencies revealed that between 10% and 25% of all trucks were overloaded.70 The Transportation Research Board later recommended increased truck weight enforcement, among other things.71 Terrell and Bell reported that majority of state officials that they surveyed perceived truck overloading to be a moderate problem.72 At that that time, it was estimated that 10 - 25% of the trucks were overloaded and that 20%of the vehicles operating on federal-aid highways had axle or gross loads in excess of statutory limits. There were annual estimates of $1 billion impacts on the cost of overloaded vehicles to the federal-aid
68
General Accounting Office. 1979. Excessive Truck Weight: An Expensive Burden We Can No Longer Support. Washington, D.C.: General Accounting Office. 69 United States Federal Highway Administration. 1995. Comprehensive truck size and weight study: Summary Report for Phase I--Synthesis of Truck Size and Weight (TS&W) Studies and Issues. Available from: http://ntl.bts.gov/DOCS/cts.html 70 Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987. 71 Transportation Research Board. 1990. Truck Weight Limits: Issues and Options. Special Report 225. 72 Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987.
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highway system.73 Since 1987, however, the numbers of roads, the volume of overweight truck traffic, and the costs associated with pavement damage have likely increased. Cottrell suggested that, in Virginia, the limited capacity of weigh stations plays a role in the number of trucks running the weigh stations. Avoidance rates at two weigh stations were examined. Eleven to fourteen percent of trucks were found to avoid weigh stations by using bypass routes or waiting until the weigh station closed. In addition, a portable WIM was used to measure the weight of trucks running weigh stations. Of the "run-by" trucks measured, 38% were classified as overweight.74 In 1994, it was found that approximately 25% of the motor vehicles that passed through weigh stations in Connecticut were illegally overweight and fined. Of these overweight vehicles, nearly 10% were identified as commercial solid waste haulers. Enforcement efforts were stepped up by equipping highway patrol units with portable scales.75 South Dakota enacted laws to prevent pavement damage from illegal overweight vehicles. In 1996, the Legislature restricted the maximum weight allowed on axles by ensuring that the weight on the axles fitted with single tires would not surpass the load capacity of the pavement. In 1999, the Legislature upped the graduated penalty schedule as a means to reduce both intentional and unintentional overweight violations.76 Cunagin, Mickler, and Wright examined Florida corridor and bypass enforcement activities through weight station avoidance. They found that the violation rate was significantly reduced through intense enforcement and that weekends were ripe for violations, when POEs were typically closed.77 In 1997, the State of Arizona Office of the Auditor General (OAG) recommended the "increase use of mobile enforcement crews along Arizona's highways." The OAG reported that MVD placed "little emphasis on intrastate enforcement." Motor carrier tax evasion was estimated to account for between $24 million to $45 million in lost potential revenue.78
Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987. 74 Cottrell, B.H., The Avoidance of Weigh Stations in Virginia by Overweight Trucks, Virginia Transportation Research Council, Charlottesville, VA, 1992. 75 Shanoff, B. 1994. Overweight Trucks Face Hefty Fines. WasteAge. Available from: http://www.wasteage.com/mag/waste_overweight_trucks_face/ 76 South Dakota Department of Transportation. 2002. SDOT Briefing: Truck Weights and Highways. 77 Cunagin, W., W. Mickler, and C. Wright. 1997. "Evasion of weight-enforcement stations by trucks." Transportation Research Record 1570, 181- 190. 78 Norton, D. R, 1997. Performance Audit: Department of Transportation Motor Vehicle Division's Revenue Functions, Report to the Arizona Legislature, Report No. 97-4. Phoenix: State of Arizona Office of the Auditor General. http://www.auditorgen.state.az.us/Reports/State_Agencies/Agencies/Transportation,%20Department%20of /Performance/97-04/97-4.pdf
73
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The challenges of weight inspections and enforcement faced each day by MVDs and Public Safety officials were best documented in a 1999 edition of the Texas Transportation Researcher. It was reported that approximately 320 Texas Department of Public Safety troopers conducted about 85,000 weight inspections each year on more than 200,000 miles of Texas highways. Dan Middleton, manager of Texas Transportation Institute System Monitoring Program, noted that "This equates to one trooper for every 45 million vehicle-miles traveled by truck in the state -- a number far too small to catch every violator.... We need a system to screen trucks in the traffic stream and identify those that have a high likelihood of being overweight... and need to be weighed statically."79 A steady increase in truck traffic, attributed to the North American Free Trade Agreement (NAFTA), results in more than $60 billion of freight -- about 70% of the total dollar value of trucking freight in the U.S. -- crossing the Texas-Mexico border.80 Although truck weights and standards comprise a part of the NAFTA plan, they do not include any provisions to raise U.S. federal or state truck size and weight limits. NAFTA does, however, lay the groundwork for Canada, Mexico, and the USA to devise compatible standards. Canada and Mexico may have longer sizes and heavier limits on their trucks. Rusfolo, et al. conducted an analysis of the weight-mile tax in Oregon to determine whether the tax influenced changes in vehicle weight or configuration that would result in decreased pavement damage. A review of the Oregon Highway User Database showed that a significant portion of mileage for the heaviest vehicles (GVW over 80,000 pounds) was reported incorrectly and was not reliable. The data were not considered conclusive and no changes could be attributed to the weight-mile tax.81 A recent sweep of waste trucks in Pennsylvania yielded 40 citations for overweight vehicles. These constituted about 10% of the waste trucks that were identified by Pennsylvania State Police.82 The Maryland State Highway Administration reports that in Maryland, there are 12 fixed Truck Weigh and Inspection Stations and seven pull-off locations. Mobile enforcement crews serve these pull-off locations. There are 22 roving enforcement teams that patrol Maryland highways. These crews enforce Federal Motor Carrier Safety Regulations and canvass the highways for those who avoid the scales.83 Two new WIM systems increased the number of vehicles weighed in Maryland by 57% in 2003. This amounted to a slight increase in the $8.5 million in fees collected through
79
Middleton, D. 1999. Keeping overweight trucks from getting a-weigh, Texas Transportation Researcher, 35:(3), 1-2. 80 Ibid. 81 Rufolo, Anthony, Lois Bronfman, Eric Kuhner, Effect of Weight-Mile Tax on Road Damage in Oregon, Oregon Department of Transportation Research Group, September 1999. 82 Pennsylvania Department of Environmental Protection. 2002. State Solid Waste Plan. Available from: http://www.dep.state.pa.us/dep/subject/advcoun/solidwst/2003/Draft_Chapter3_Municipal%20Waste.pdf 83 Maryland State Highway Administration, Office of Traffic and Safety, Motor Carrier Division. 2003. 2003 Annual Report: Maryland Motor Carrier Program.
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oversize/overweight permits each year. A review of the data of weight enforcement activities from 1998 to 2003 shows that more vehicles are weighed on fixed scales than on WIMs. However, with the addition of two new WIMs in strategic locations, not only is there a dramatic increase in the number of vehicles weighed on WIMs, but also a difference of nearly 10,000 vehicles weighed between the static and the WIM scales. Additionally, an Automated Hauling Permit System is used for permit issuance. This not only involves a smaller staff to operate, but it also provides a faster turnaround time for permit applications.84 In Maryland, trucks deliver nearly 81% of all manufactured freight. They are vital to the economy because they can "access 92% of the state's communities without special accommodation."85 In North Carolina, in 2005, ".... more than 100 vacancies in the ranks of weight enforcement officers and the patrol's lack of emphasis on catching overweight trucks"86 halved the overweight truck citations in the span of 5 years. Legislators responded by earmarking monies to the North Carolina Highway Patrol to increase the number of weight enforcement officers and improve its activities. Another challenge for law enforcement officers is the presence of large trucks on roads other than highways. Large trucks are already a hot button in some residential communities. In Tucson, Arizona, for example, an increase in pollution, noise, and pavement damage led Rincon Valley residents to petition to limit the size of trucks on the streets to those with a 3/4-ton rear-axle load capacity. While Pima County officials review the policy of imposing a strict weight limit on residential streets, they are unable to enforce it because there are no scales and roving weight enforcement officers on the beat in residential communities in Tucson.87 Other cities across Arizona and the U.S. face similar obstacles as the volume of traffic escalates over the next 50 years and spills from the highways and unto the residential roads. ESRA obtained data on ratios of total overweight permits issued and overweight vehicle violations to heavy truck traffic (see Tables 16 and 17). All data, for the year 2003, were obtained through the DOT/FHWA websites. The permits include the total "number of overweight permits issued by States for non-divisible and divisible single trip load movements, non-divisible and divisible annual (or multiple use) load movements, and for divisible over-width load movements."88 According to the DOT/FHWA, the state weight violations include the total "number of trucks cited or issued civil assessments by the
Maryland State Highway Administration, Office of Traffic and Safety, Motor Carrier Division. 2003. 2003 Annual Report: Maryland Motor Carrier Program. 85 Ibid. 86 Stith, P. 2005. "Troopers ticketing more heavy trucks." The News and Observer. Published 17 August 2005. Available from: < http://newsobserver.com/news/story/2728787p-9166402c.html> 87 Ellis, T. 2004. "Big trucks an issue on residential streets." Arizona Daily Star. Published 5 June 2004. Available from: <http://www.azstarnet.com/dailystar/relatedarticles/24949.php> 88 United States Department of Transportation, Federal Highway Administration. 2005. Freight Management and Operations: Permit Facts and Figures FY 2003. Available from: http://ops.fhwa.dot.gov/freight/sw/permit_report.htm
84
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States for violation of weight laws. Also included are the numbers of trucks that were required to off load or shift their load to be in compliance with the weight laws."89 Table 16: State Permits and Weight Violations, Fiscal Year 2003*
Total Total VMT Permits/ Violations/ Permits/ Violations/ overweight overweight heavy Heavy 1,000 1,000 million million permits vehicle trucks Trucks issued violations (millions) (1,000s) trucks trucks VMT VMT 25,507 17,693 2,575 54.8 9.9 6.9 465.5 322.9 7,058 587 109 5.9 64.8 5.4 1196.3 99.5 83,651 28,457 1,380 31.5 60.6 20.6 2655.6 903.4 38,787 10,597 482 22.1 80.5 22.0 1755.1 479.5 197,750 77,735 6,889 200.3 28.7 11.3 987.3 388.1 15,764 22,077 367 29 43.0 60.2 543.6 761.3 64,615 6,714 535 21.1 120.8 12.5 3062.3 318.2 175,281 372 183 6.5 957.8 2.0 26966.3 57.2 1,578 271 1 0.1 1578.0 271.0 15780.0 2710.0 2,477 76.5 0.0 0.0 0.0 0.0 69,528 51,009 1,094 50.2 63.6 46.6 1385.0 1016.1 2,767 1,248 77 5.2 35.9 16.2 532.1 240.0 61,444 14,429 1,471 56.8 41.8 9.8 1081.8 254.0 133,619 71,584 11,191 177.5 11.9 6.4 752.8 403.3 207,609 10,937 4,552 95.3 45.6 2.4 2178.5 114.8 30,544 16,407 976 45.2 31.3 16.8 675.8 363.0 43,386 20,104 1,404 52.8 30.9 14.3 821.7 380.8 86,380 7,020 1,025 40.3 84.3 6.8 2143.4 174.2 85,487 62,811 693 25.5 123.4 90.6 3352.4 2463.2 19,373 1,901 231 11 83.9 8.2 1761.2 172.8 145,160 21,827 290 15.8 500.6 75.3 9187.3 1381.5 69,939 5,715 898 29.8 77.9 6.4 2346.9 191.8 123,492 5,503 2,528 80.3 48.8 2.2 1537.9 68.5 24,180 3,902 2,536 68.4 9.5 1.5 353.5 57.0 137,057 24,969 675 13.3 203.0 37.0 10305.0 1877.4 43,997 22,006 2,880 68.6 15.3 7.6 641.4 320.8 13,585 8,203 154 17.4 88.2 53.3 780.7 471.4 54,186 22,925 2,852 54.3 19.0 8.0 997.9 422.2 18,514 1,007 263 10.1 70.4 3.8 1833.1 99.7 2,160 314 12.6 6.9 171.4 9,592 2,826 2,807 75.9 3.4 1.0 126.4 37.2 17,881 1,329 323 13.1 55.4 4.1 1365.0 101.5 193,970 9,551 1,767 79.7 109.8 5.4 2433.8 119.8 72,493 32,999 4,327 103.7 16.8 7.6 699.1 318.2 49,794 17,759 35 35.2 1422.7 507.4 1414.6 504.5
State Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware DC Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota
United States Department of Transportation, Federal Highway Administration.. 2005. State Information on Citation and Civil Assessments Issued for Overweight Violations: State Weight Violation Facts and Figures FY 2003. Available from: http://ops.fhwa.dot.gov/freight/sw/violation_report.htm, and U.S. Census Bureau, Vehicle Inventory and Use Survey, http://www.census.gov/svsd/www/02vehinv.html.
89
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State Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming Total
Total Total VMT Permits/ Violations/ Permits/ Violations/ overweight overweight heavy Heavy 1,000 1,000 million million permits vehicle trucks Trucks issued violations (millions) (1,000s) trucks trucks VMT VMT 120,775 24,808 4,609 118.5 26.2 5.4 1019.2 209.4 37,541 1,847 19,428 233.4 1.9 0.1 160.8 7.9 132,381 22,179 615 16 215.3 36.1 8273.8 1386.2 112,140 1,453 737 44 152.2 2.0 2548.6 33.0 15,328 238 91 3.7 168.4 2.6 4142.7 64.3 54,712 12,170 1,516 31 36.1 8.0 1764.9 392.6 43,443 6,374 646 22.6 67.2 9.9 1922.3 282.0 104,081 8,558 2,963 59.1 35.1 2.9 1761.1 144.8 193,320 71,745 7,616 164 25.4 9.4 1178.8 437.5 20,286 11,320 1,489 25.2 13.6 7.6 805.0 449.2 26,785 1,256 260 8.4 103.0 4.8 3188.7 149.5 79,954 136,120 1,704 44.6 46.9 79.9 1792.7 3052.0 139,369 17,944 1, 3 3 3 41.5 104.6 13.5 3358.3 432.4 71,036 3,344 699 21.7 101.6 4.8 3273.5 154.1 21,109 8,175 2,653 61.3 8.0 3.1 344.4 133.4 48,221 2,275 279 11 172.8 8.2 4383.7 206.8 3,544,449 934,440 106,999 2,592 33.1 8.7 1367.6 360.5
*Sources: DOT/FHWA, 2005; VMT = vehicle miles of travel and United States Census Bureau, http://www.census.gov/svsd/www/02vehinv.html We find that Arizona has a higher ratio of permits and violations per heavy truck vehiclemile of travel (VMT) and per registered heavy truck compared to the average of all the states. This supports the premise that overweight trucks are more prevalent in Arizona than most other states. However, a nationwide comparison may not be as relevant as a neighboring state comparison. Interstate trucks traveling through Arizona also travel in the neighboring states. A vehicle that is overweight in one state is likely overweight when it enters a neighboring state. Table 17 shows overweight permits and violations for Arizona and its neighboring states.
52
Table 17: Arizona & Neighboring State Permits & Weight Violations, FY 2003
Total Total VMT overweight overweight heavy Heavy Permits/ Violations/ Permits/ Violations/ 1,000 1,000 million million permits vehicle trucks Trucks issued violations (millions) (1,000s) trucks trucks VMT VMT 83,651 28,457 1,380 31.5 60.6 20.6 2,655.6 903.4 197,750 77,735 6,889 200.3 28.7 11.3 987.3 388.1 15,764 22,077 367 29.0 42.9 60.1 543.6 761.3 18,514 1,007 263 10.1 70.4 3.8 1,833.1 99.7 17,881 1,329 323 13.1 55.4 4.1 1,365.0 101.5 20,286 11,320 1,489 25.2 13.6 7.6 805.0 449.2 353,846.0 141,925 10,711 309.2 33.0 13.3 1,144.4 459.0
State Arizona California Colorado Nevada New Mexico Utah Total
Table 17 indicates that Arizona is selling more overweight permits per heavy truck VMT and per registered heavy truck than most of its neighboring states. This evidence implies that Arizona is relatively aggressive in its efforts to induce overweight vehicles to purchase permits. In terms of overweight violations, Arizona issues more citations than most of its neighboring states. This evidence may suggest that Arizona is also relatively aggressive in catching violators at its state and national borders. These data may suggest that Arizona extracts greater revenues from overweight trucks and catches more trucks that evade the permit fees than neighboring states are. Further studies are needed to determine if these data can be correlated with interstate trucks moving across state lines since many states have passed weight exemptions for local industries. Hence a lack of enforcement may be a matter of state law90. According to FHWA estimates, urban areas and the Interstate Highway System will account for the bulk of truck traffic growth anticipated in Arizona over the next 15 years (see Appendix A), particularly along I-10.91 Clearly, continuous maintenance of the state's highway infrastructure is a necessity. Carey estimates that vehicles in the heaviest weight class, i.e., those registered at 75,000 lbs. and over, underpay state taxes and fees by the widest margin, irrespective of the highway cost allocation model employed.92 Using Carey's simplified model, the Arizona Department of Transportation's Financial Management Section estimates that these vehicles impose approximately $35 million per year in uncompensated pavement wear.93 This implies there is a substantial amount of evasion of overweight vehicle regulations. Such challenges lead Strathman and Theisen to support weight violation penalties that "...effectively relate the economic incentives to overload and the consequential damage to roadways."94
Anonymous TRB reviewer, October 2005. Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 92 Carey, J. 2001. Implementation of the Simplified Arizona Highway Cost Allocation Study Model. FHWAAZ-01-477(3). Phoenix, Arizona: Arizona Department of Transportation. 93 Arizona Department of Transportation, Financial Management Section, internal report, June 21, 2005. 94 Strathman, J. G. and G. Theisen. 2002. Weight Enforcement and Evasion: Oregon Case Study. FHWAOR-DF-02-12. Salem, Oregon: Oregon Department of Transportation.
91
90
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VI. PAVEMENT DAMAGE ESTIMATION Initially, ESRA pored over WIM data collected over several years across different Arizona ports. This data was to be used to try to quantify the pavement damages associated with overweight

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Estimating the Cost of Overweight Vehicle Travel on Arizona Highways
Final Report 528
Prepared by: Sandy H. Straus ESRA Consulting CorporationTM rd 1650 South Dixie Highway, 3 Floor Boca Raton, Florida 33432 shs@esracorp.com John Semmens Arizona Department of Transportation th 206 S. 17 Avenue Phoenix, Arizona 85007
JANUARY 2006
Prepared for: Arizona Department of Transportation 206 South 17th Avenue Phoenix, Arizona 85007 in cooperation with U.S. Department of Transportation Federal Highway Administration
The contents of the report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The authors assume no liability for the use or misuse of any information, opinions, or conclusions contained in this report. The contents do not necessarily reflect the official views or policies of the Arizona Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Trade or manufacturers' names which may appear herein are cited only because they are considered essential to the objectives of the report. The U.S. Government and The State of Arizona do not endorse products or manufacturers.
Technical Report Documentation Page
1. Report No. 2. Government Accession No.
3. Recipient's Catalog No.
FHWA-AZ-06-528
4. Title and Subtitle 5. Report Date
January 2006
Estimating the Cost of Overweight Vehicle Travel on Arizona Highways
7. Authors
6. Performing Organization Code
8. Performing Organization Report No.
Sandy H. Straus and John Semmens
9. Performing Organization Name and Address 10. Work Unit No.
Sandy H. Straus ESRA Consulting Corporation 1650 South Dixie Highway, Third Floor Boca Raton, Florida 33432 (561) 361-0004 http://www.esracorp.com
11. Contract or Grant No.
SPR-PL-1-(59) 528
12. Sponsoring Agency Name and Address 13.Type of Report & Period Covered
ARIZONA DEPARTMENT OF TRANSPORTATION 206 S. 17TH AVENUE PHOENIX, ARIZONA 85007 Project Manager: John Semmens
15. Supplementary Notes
14. Sponsoring Agency Code
Prepared in cooperation with the U.S. Department of Transportation, Federal Highway Administration
16. Abstract
This study quantifies state highway damage on the basis of the impacts of overweight vehicles. Each year, millions of dollars of damage associated with life span, design, and maintenance of state highways and structures are attributed to vehicles that exceed state weight limits. Our best guess is that overweight vehicles impose somewhere between $12 million and $53 million per year in uncompensated damages to Arizona roadways. Arizona currently budgets about $5.8 million per year for mobile enforcement efforts aimed at, among other things, penalizing and deterring overweight vehicle operations. If a doubling of the mobile enforcement budget were 50% effective toward the objective of eliminating illegally overweight vehicles from Arizona roadways, the savings from avoided pavement damage would range from $6 million to $27 million per year. At the lower figure, the expansion of mobile enforcement would be a little better than a "break-even" proposition. The savings from avoided pavement damage would slightly exceed the cost of the program. Any safety gains from detecting and taking out-of-service vehicles with safety deficiencies would come on top of the pavement damage avoidance gains. At the higher figure, the expansion of mobile enforcement would have about a four- or five-toone benefit/cost ratio. That is, for every dollar invested in motor carrier enforcement efforts, there would be $4.50 in pavement damage avoided. Furthermore, we introduce a new truck lane design that may ultimately improve safety and optimize pavement usage in Arizona and other states.
17. Key Words 18. Distribution Statement 23. Registrant's Seal
Pavement damage, mobile enforcement, overweight vehicle, Arizona ports, pavement fatigue, US border, overweight truck, heavy truck, highway impacts, road damage, truck lanes, truck-only lanes, automation, highway cost estimate, pavement damage estimate, truckways, ESRA SPDE, weigh station, WIM
19. Security Classification 20. Security Classification
Document is available to the U.S. public through the National Technical Information Service, Springfield, Virginia 22161
21. No. of Pages 22. Price
Unclassified
Unclassified
81
SI* (MODERN METRIC) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS
Symbol When You Know Multiply By To Find Symbol Symbol
APPROXIMATE CONVERSIONS FROM SI UNITS
When You Know Multiply By To Find Symbol
LENGTH
in ft yd mi inches feet yards miles 25.4 0.305 0.914 1.61 millimeters meters meters kilometers mm m m km mm m m km millimeters meters meters kilometers
LENGTH
0.039 3.28 1.09 0.621 inches feet yards miles in ft yd mi
AREA
in ft2 yd2 ac mi2 fl oz gal ft3 yd3
2
AREA
square millimeters square meters square meters hectares square kilometers milliliters liters cubic meters cubic meters
3
square inches square feet square yards acres square miles fluid ounces gallons cubic feet cubic yards
645.2 0.093 0.836 0.405 2.59
mm m2 m2 ha km2 mL L m3 m3
2
mm m2 m2 ha km2 mL L m3 m3
2
Square millimeters Square meters Square meters hectares Square kilometers milliliters liters Cubic meters Cubic meters
0.0016 10.764 1.195 2.47 0.386
square inches square feet square yards acres square miles fluid ounces gallons cubic feet cubic yards
in2 ft2 yd2 ac mi2 fl oz gal ft3 yd3
VOLUME
29.57 3.785 0.028 0.765
VOLUME
0.034 0.264 35.315 1.308
NOTE: Volumes greater than 1000L shall be shown in m .
MASS
oz lb T ounces pounds short tons (2000lb) 28.35 0.454 0.907 grams kilograms megagrams (or "metric ton") Celsius temperature g kg mg (or "t")
?
MASS
g kg Mg grams kilograms megagrams (or "metric ton") Celsius temperature 0.035 2.205 1.102 ounces pounds short tons (2000lb) oz lb T
TEMPERATURE (exact)
?
TEMPERATURE (exact)
C
?
F
Fahrenheit temperature foot candles foot-Lamberts poundforce poundforce per square inch
5(F-32)/9 or (F-32)/1.8
C
1.8C + 32
Fahrenheit temperature foot-candles foot-Lamberts poundforce poundforce per square inch
?
F
ILLUMINATION
fc fl lbf lbf/in2 10.76 3.426 4.45 6.89 lux candela/m2 newtons kilopascals lx cd/m2 N kPa lx cd/m2 N kPa lux candela/m2 newtons kilopascals
ILLUMINATION
0.0929 0.2919 0.225 0.145 fc fl lbf lbf/in2
FORCE AND PRESSURE OR STRESS
FORCE AND PRESSURE OR STRESS
SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380
ESRA CONSULTING CORPORATION DISCLAIMER
Neither ESRA Consulting Corporation (ESRA), its affiliates, its associates, nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. References herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by ESRA or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of ESRA or any agency thereof. This report is for informational purposes only. Readers are encouraged to confirm the information contained herein with other sources. Reliance on any information in this report is solely at your own risk. ESRA Consulting Corporation is not responsible or liable for any direct, indirect, consequential, special, exemplary, or other damages arising from any use of any product, information, idea, or instruction contained in this report and all publications and presentations and/ or implementations therefrom. Notice is hereby provided that a patent application has been filed on one or more of the systems and methods described herein. Notice is hereby provided that ESRA may be involved in development and/ or marketing of products in the systems and/ or methods described herein. In the event that consideration is given to any component in the system described herein in which ESRA may have a marketing arrangement or other involvement, at the time of such consideration, full disclosure will be made.
I dedicate this report to the memory of my grandfather, Bernard, whose fascinations with the realms of transportation and automation were an inspiration to me. I always miss him. -SHS
TABLE OF CONTENTS
EXECUTIVE SUMMARY ............................................................................................................ 1 INTRODUCTION .......................................................................................................................... 3 I. FEDERAL TRUCK SIZE AND WEIGHT LIMITS ................................................................ 5 History............................................................................................................................................. 5 Current Federal Laws and Proposals .............................................................................................. 6 Highway Safety Implications.......................................................................................................... 6 The Feasibility of Truck-only Lanes............................................................................................... 6 II. MAGNITUDE OF OVERWEIGHT VEHICLE IMPACTS ................................................... 9 Pavement Types .............................................................................................................................. 9 Pavement Design ............................................................................................................................ 9 Pavement Maintenance and Life Span.......................................................................................... 10 Pavement Fatigue.......................................................................................................................... 10 Bridges and the Federal Bridge Formula ...................................................................................... 12 Pavement Costs............................................................................................................................. 14 The Significance of Fuel Taxes in Arizona and Other U.S. States............................................... 14 Pavement Cost Methods ............................................................................................................... 15 III. IDENTIFICATION OF OVERWEIGHT TRAFFIC ........................................................... 17 Manual and Automated Traffic Counting Techniques ................................................................. 17 Weigh-in-motion Sensors ............................................................................................................. 18 Traffic Data Collection Methods in Arizona ................................................................................ 19 IV. SURVEY OF TRANSPORTATION OFFICIALS AND/OR TRUCK ENFORCEMENT PERSONNEL FROM SEVERAL U.S. STATES AND CANADA .............. 23 Introduction................................................................................................................................... 23 Survey Responses ......................................................................................................................... 24 Conclusions................................................................................................................................... 45 V. THE CHALLENGE OF OVERWEIGHT VEHICLE ENFORCEMENT ............................. 47 VI. PAVEMENT DAMAGE ESTIMATION.............................................................................. 55 VII. CONCLUSIONS ................................................................................................................... 59 REFERENCES ............................................................................................................................. 61 APPENDIX A: ARIZONA FREIGHT FLOWS BY TRUCK AND ESTIMATED ANNUAL DAILY TRUCK TRAFFIC ........................................................................................ 67 APPENDIX B: TOP FIVE COMMODITIES SHIPPED TO, FROM, AND WITHIN ARIZONA..................................................................................................................................... 71 APPENDIX C: TRUCK CONFIGURATION, WEIGHT, AND FUEL ECONOMY................ 72
TABLES page Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 Table 12 Table 13 Table 14 Table 15 Table 16 Table 17 Table 18 Measured or estimated percentage of in-state travel comprised of vehicles exceeding legal limits (gross or axle or both) on weight Estimated cost of overweight vehicle damage Percentage of trucks on roads weighed at ports-of-entry Typical hours of operation for ports-of-entry Amount budgeted for mobile enforcement units on an annual basis Amount of mobile enforcement unit person-hours on an annual basis Quantity of vehicles weighed by mobile enforcement units/year Percentage of weighed vehicles exceeding legal limits through mobile enforcement units Average estimated number of pounds (lbs.) over the legal limit as reported by mobile enforcement units Some actions taken by state officials to reduce pavement damage Summaries of desired actions that are unfunded due to financial and other impediments The locations where most weight violations occur Time when most weight violations occur Classes and number of axles of vehicles that have the highest rate of in-state overweight violations Ratio of overweight permits you issue to overweight vehicle violations State Permits and Weight Violations, Fiscal Year 2003 Arizona & Neighboring State Permits & Weight Violations, FY 2003 Estimates of the Percentage of Overweight Vehicles FIGURES Page Figure 1 Figure 2 Typical hours of operation for ports-of-entry in selected states Amount of person-hours assigned to the duty of mobile enforcement units on a statewide annual basis in selected states 29 33 24 25 27 28 31 34 35 36 37 38 39 41 42 43 44 51 53 57
GLOSSARY OF ACRONYMS
AADT AASHTO ADOT ATPD ATRC AVC ESRA EVOC FHWA FBF GAO GVW IFTA IRP LCV LDOTD LTPP MCSAP MNDOT MVD NHTSA NN OAG SPDE TRB TRIP US USA USDOT VIUS WIM
Average Annual Daily Traffic American Association of State Highway and Transportation Officials Arizona Department of Transportation Arizona Transportation Planning Division Arizona Transportation Research Center Automatic Vehicle Classification ESRA Consulting Corporation Extra Vehicle Operating Costs Federal Highway Administration Federal Bridge Formula General Accounting Office Gross Vehicle Weight International Fuel Tax Agreement International Registration Plan Longer Combination Vehicle Louisiana Department of Transportation and Development Long Term Pavement Performance Motor Carrier Safety Assistance Program Minnesota Department of Transportation Motor Vehicle Division National Highway Traffic Safety Administration National Network State of Arizona Office of the Auditor General Straus Pavement Damage Estimation Transportation Research Board The Road Information Program United States United States of America United States Department of Transportation Vehicle Inventory and Use Survey (United States Census Bureau) Weigh-in-Motion
EXECUTIVE SUMMARY In order to quantify state highway damage, we seek to identify and evaluate the impacts of overweight vehicles on pavement. Since ancient times, pavements have played a vital role in trade and transportation throughout the world. Today, in the State of Arizona, the Arizona Department of Transportation (ADOT) and the ADOT Motor Vehicle Division (MVD) undertake the burden of law enforcement policies and activities associated with size and weight of vehicles on Arizona highways. Each year, overweight vehicles account for millions of dollars of damage connected with the life span, design, and maintenance of state highways and structures. Improvements are now needed on the roads and at all of the 22 Arizona ports in order to maintain the state's role as an economic powerhouse for freight activity in the years to come. Consequently, the results of this study may not only benefit the State of Arizona, but also other states and countries that face escalating costs associated with pavement fatigue and overweight vehicle enforcement challenges. Through survey techniques and a canvass of the literature, we identify the methods and expenditures that other states use for overweight vehicle issues and mobile enforcement units. We also introduce a unique truck lane design to aid mobile enforcement agents and minimize pavement damage. Arizona currently budgets about $5.8 million per year for mobile enforcement efforts aimed at, among other things, penalizing and deterring overweight vehicle operations in nearly 113,642 square miles of Arizona land area. The ADOT Simplified Highway Cost Allocation Model allows us to estimate that illegally overweight vehicles impose somewhere between $12 million and $53 million per year in uncompensated damages to Arizona roadways. The ADOT Simplified Highway Cost Allocation Model estimates that savings from avoided pavement damage would range from $6 million to $27 million per year if a doubling of the mobile enforcement budget were 50% effective toward the objective of eliminating illegally overweight vehicles from Arizona roadways. At the lower figure, the expansion of mobile enforcement would be a small improvement over a "break-even" proposition. The savings from avoided pavement damage would slightly exceed the cost of the program. Any safety gains from detecting and taking out-of-service vehicles with safety deficiencies would come on top of the pavement damage avoidance gains. At the higher figure, the expansion of mobile enforcement would have about a four- or five-toone benefit/cost ratio. That is, for every dollar invested in motor carrier enforcement efforts, there would be $4.50 in pavement damage avoided.
1
2
INTRODUCTION Pavement fatigue is proportional to repetitive loadings. These loadings, attributed to traffic growth, generate pavement damage at earlier, faster, and costlier rates. The volume of truck traffic increases rapidly as the Interstate Highway System becomes available and popular. The overloaded truck, whether legal or illegal, contributes to premature pavement fatigue. These challenges lead to the need to develop new methods of pavement damage estimation and fatigue reduction techniques. The estimation of damage to state highway systems by overweight vehicles involves several variables. These may include the following, when available: ? ? ? ? ? ? ? Traffic counts for various segments, categorized by vehicle configuration. Weigh-in-motion (WIM), bridge and static scale measures for vehicles of various configurations. Highway spending related to overweight vehicle traffic. Commercial vehicle permits and/or registrations by weight class and configuration. Weight distance tax collections for years prior to the repeal of this tax. Weight citations recorded by state enforcement personnel. Diesel fuel consumption data1.
Overweight vehicle enforcement remains a problem in most U.S. states. As our survey demonstrates, the port and mobile enforcement crews are understaffed and/or under funded. Some lack qualifications or skills necessary to adequately detect and monitor overweight trucks. There are few ports equipped with cutting edge technology to adequately identify overweight truck violations. Ernzen reports that some ports are closed more hours than they are open.2 These circumstances lead to an inadequate enforcement of penalties for illegal overloads. Operators of illegally overloaded vehicles may also escape fines due to the failure of the judicial or administrative procedures dealing with detected violators. Billions of dollars are spent each year to replace and repair U.S. highways. Fines for illegal overloading are, therefore, not often correlated with the actual cost of pavement damage. Effectively monitoring and controlling truck weights are paramount to road preservation and minimization of pavement costs. Ultimately, the regulations that U.S. states uphold are intended to balance the economic benefits of commercial vehicle operations, particularly through large trucks. Nearly everything we own, eat, use, grow, or manufacture is carried by truck at least part of its
1 2
Straus, S. H. 2005. pending publication. Ernzen, J. M. 2005, Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
3
journey. Trucks transport nearly three-fourths of the value and nearly two-thirds of the tonnage of all manufactured goods and raw materials shipped across the USA.3 Trucks are vital to the economy; illegal overweight trucks are not.
3
General Accounting Office . 2005. Large Truck Safety: Federal Enforcement Efforts Have Been Stronger Since 2000, but Oversight of State Grants Needs Improvement. GAO-06-156. Washington, D.C.
4
I.
FEDERAL TRUCK SIZE AND WEIGHT LIMITS
History Federal Law regulates truck size and weight limits on interstate highways, national forests, national parks, and other federal lands. Some exceptions include those standards by "grandfather" right and provision for special permits.4 The Surface Transportation Assistance Act (STAA) of 1982 requires U.S. states to allow larger trucks on the National Network, which is comprised of the Interstate system plus the non-Interstate Federal-aid Primary System. All Federal and state laws, directly or indirectly, affect the quality and performance of pavement on our nation's highways. In 1941, Congress directed the Interstate Commerce Commission (ICC) to consider federal regulation of the sizes and weights of freight-carrying motor vehicles that were involved in interstate or international commerce. In 1956, the Federal Government initiated a program to regulate truck size and weight limits in order to improve federal investments in the Interstate Highway System. According to the DOT (2000): "A maximum gross weight limit of 73,280 pounds was established along with maximum weights of 18,000 pounds on single axles and 32,000 pounds on tandem axles. Maximum vehicle width was set at 96 inches.... States having greater weight or width limits... were allowed to retain those limits under a grandfather clause." 5 In 1975, a spike in fuel costs led the Congress to increase the allowable gross weight and axle weight limits. The U.S., through the STAA of 1982 (P.L. 97-424), adopted federal weight limits on Interstate Highways. Large trucks, such as 48-foot long semi-trailers, among others with prescribed minimum dimensions, were to be allowed on a National Network. A freeze on the expansion of operations on long combination vehicles followed in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) (P.L. 102-240). The Comprehensive Truck Size and Weight Study6 thoroughly examines issues associated with potential modifications of the current Federal truck size and weight (TS&W) limits. These include a foundation for cost and benefit analyses. In U.S. states, overweight permits are typically issued to routine overweight trucks. Fees are charged for these permits. These are intended to correspond to the additional infrastructure costs associated with the overweight vehicle. Sometimes these fees may cover only administrative costs of permit issuance. When moves often require special equipment and routing, permits may be issued for transports that involve heavier loads.
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 5 Ibid. 6 Ibid.
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Current Federal Laws and Proposals Federal law currently includes the following limits: ? ? ? 20,000 pounds for single axles on the Interstate System. 34,000 pounds for tandem axles on the Interstate System. Application of the Federal Bridge Formula for other axle groups up to the maximum of 80,000 pounds gross vehicle weight on the Interstate System.
Tandem axles are generally defined as two or more consecutive axles that are more than 40 inches but not more than 96 inches apart.7 From time to time, there have been proposals to increase the federal truck size and weight limits. Such proposals are controversial. Additional infrastructure costs, disruption of traffic flow, financial impacts on competing railroads, and potential adverse impacts on safety are all possible byproducts of increasing federal truck size and weight limits. As distance increases, rail appears as the preferred method of transportation. It is impossible to predict the extent to which U.S. states would allow larger and heavier vehicles to operate if no uniform nationwide criteria were in place. Yet, pavement quality and performance characteristics are ultimately shaped by truck size and weight policies. Trucks exert loads and vehicle forces on pavement. Therefore, pavement design must account for load distribution. Traffic volume, tire loads, axle configuration, vehicle speed, tire configuration, and load repetition, among others, all affect pavement. Highway Safety Implications Truck volume is a function of Federal truck size and weight restrictions. An increase in truck volume, especially among the very large and overweight motor carriers, compromises the safety of other motorists. Trucks contribute to congestion, traffic delays, and pavement fatigue. These increase the likelihood of a collision, injury, or fatality on the nation's highways. Overweight vehicles not only create infrastructure damage issues, but safety risks as well.8 The Feasibility of Truck-only Lanes Over the last 20 years, the volume of combination vehicles has doubled. By 2020, commercial truck travel may increase significantly and surpass all other vehicle travel in the U.S. Truck-only lanes are being proposed on some U.S. highways to accommodate the demand for large truck and commercial travel. These lanes, typically separate from high-speed traffic and other mixed-flow traffic, are allowed for the exclusive use of trucks. Few truck-only lanes exist in the USA. While trucks are restricted to certain
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Arizona State Legislature. 2005. The Arizona Revised Statutes , 28-1100. Vehicles and loads; gross weight restrictions; exception. 46th Legislature, 2nd regular session. 8 Weight Tolerance Permits, Research Report 1323-2F, Texas Transportation Institute, Texas A&M University System and Texas Department of Transportation, 1994.
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lanes in most states, all vehicles are permitted use of the same lanes. According to a recent feasibility study conducted for the California Department of Transportation (CALTRANS), "....exclusive truck lanes were the most plausible for congested highways where three factors exist: (1) truck volumes exceed 30% of the vehicle mix, (2) peak hour volumes exceed 1,800 vehicles per lane-hour, and (3) off-peak volumes exceed 1,200 vehicles per lane-hour."9 The construction of truck-only lanes may ultimately improve safety and reduce traffic congestion. According to The Road Information Program (TRIP),10 National Highway Traffic Safety Administration (NHTSA) data from U.S. highways from 1998 to 2002 seem to support truck-only lane proposals. One-lane traffic fatalities involving large trucks account for about 0.5% of traffic fatality collisions in all lanes. Large truck traffic fatalities are highest in two lanes (75.5%) and four lanes (12.2%). Fatalities involving large trucks are greatest where the posted speed limit is 55 mph (37.8%) and 60 mph or higher (35%). The lower the posted speed limit, the fewer the number of large truck fatalities. In Arizona, an average of 100 people are killed in large-truck collisions each year. Samuel et al.11 present an interesting concept of "self-financing inter-city toll truckways," where heavy truck lanes are fitted with continuous concrete safety barrier(s) and "dedicated ingress and egress ramps and staging areas." A truckway is envisaged to exist "....either in its own right of way separate from any other roadway or located within the right of way of a limited-access highway, but which is completely separated from the mixed traffic lanes... and... fully grade separated and access controlled and may be one or two lanes in each direction." However, these custom-built and designed truck "freeways within-the-freeway" would involve considerable time and expense to construct. In-depth safety and economic analyses would be needed to prove such feasibility for the following reasons, among others: ? ? Jersey barriers or concrete traffic dividers are typically designed to minimize damage and reduce the likelihood of a car crossing into oncoming lanes in the event of a collision.12 Collisions that could occur in such truck "freeways within-the-freeway" could not only cost lives but additional collisions since heavy truck drivers would not have
California Department of Transportation (CALTRANS). 2004. "Truck-Only Lanes." CALTRANS: Traffic Operations Program, Office of Truck Services. May 24, 2004. < http://www.dot.ca.gov/hq/traffops/trucks/trucksize/fs-trucklanes.htm> 10 The Road Information Program. 2004. America's Rolling Warehouses: The impact of increased trucking on economic development, congestion, and traffic safety. http://www.tripnet.org/TruckingReport020904.PDF 11 Samuel, P., R. W. Poole, Jr., and J. Holguin-Veras. 2002. Toll Truckways: A New Path Toward Safer and More Efficient Freight Transportation. Policy Study 294. Los Angles, California: Reason Public Policy Institute. 12 McDevitt, C. 2000. "Basics of Concrete Barriers." In Public Roads. March/ April 2000. Volume 63. Number 5. Available from:
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the option to easily switch to one or more traffic lanes in the event of an emergency or to avoid a bottleneck. Concrete barriers of various dimensions, specifically heights and thicknesses, as well as different mechanisms of reinforcement and shapes, may be required for safety purposes.
Of all the states, Arizona demonstrates the highest percentage increase (78%) in large truck travel over the 1998 to 2002 period. Large trucks pose a significant economic cost due to accelerated fatigue on the pavement. The pavement fatigue also increases vehicle wear that may impact vehicular performance and maintenance costs. Consequently, truck-only lanes might reduce the high costs associated with pavement maintenance and replacement. The accelerated pavement fatigue might then be limited to the truck-only lanes rather than all of the other lanes shared with all other motorists. The truck-only lanes would also aid roving enforcement agents in identification and tracking of suspect overweight vehicles. Truck-only lanes may not only prove to be a safe choice, but an economically feasible one as well. We, therefore, introduce truck-only lane designs13 that may be equipped with special sensors to allow mobile enforcement crews to remotely detect the presence of overweight trucks. These designs, as developed by ESRA Consulting Corporation TM, offer a significant and cost-effective improvement over others. Such lanes may be created within new or existing lanes to reduce costs. All trucks may drive on these lanes and therefore limit excess pavement damage to these lanes. Tolls may be an option based on the penalties assessed to illegally overweight truck drivers. Some states, however, may eventually add tolls to truck only lanes. Since these lanes are not fitted with any special sensors as we prescribe, all heavy truckers would be levied a toll. Therefore, our truckonly lane designs may ultimately improve safety, optimize pavement design, and strike a balance between the trucking industry, our government, and stakeholders. Since the safety implications of any new or existing lane construction requires consideration, further studies are now needed to aid in the development of truck-only lanes in Arizona and other states. However, their study, development, and implementation will not be possible without policy reforms by the state and federal government.
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For more information about these truck-only lane designs, please contact Sandy H. Straus, ESRA Consulting Corporation, 1650 South Dixie Highway, Third Floor, Boca Raton, Florida 33432, Telephone: 561-361-0004, e-mail: trucks@esracorp.com.
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II.
MAGNITUDE OF OVERWEIGHT VEHICLE IMPACTS
Pavement Types Flexible and rigid pavements are the two primary types of hard surfaced pavements. Flexible pavements are the most common. These cover 93% of all U.S. roads. Bituminous (asphalt) materials comprise flexible pavements. These are "flexible" because the traffic loads cause the total pavement structure to "bend" or "deflect." Flexible pavement design allows surface load stress to wane with depth. A layered system with progressively weaker materials generally provides adequate strength to resist the load stress. Pavements comprised of Portland cement concrete (PCC) have high stiffness and are therefore referred to as "rigid."14 The distribution of load over a subgrade, "the suspension system" of the pavement varies according to pavement type.15 However, pavement structure, mix design, and subgrade all influence the life and performance of the pavement. Pavement Design The design and analysis of pavement structures are primarily dependent upon traffic data. The American Association of State Highway and Transportation Officials (AASHTO) pavement damage equivalency equations and Highway Performance Monitoring System (HPMS) pavement functions govern the use and application of such data. Various procedures are used and identified in the 1993 AASHTO Guide for Design of Pavement Structures.16 For example, it is possible to convert a mixed traffic stream of different axle loads and axle configurations into a design traffic number. This can be achieved by converting each expected axle load into an equivalent number of 18 kipsingle-axle loads, known as equivalent single-axle loads (ESALs). The AASHTO damage concept, however, has some limitations. According to the Texas Transportation Institute, the AASHTO damage concept is based on a serviceability index.17 Some significant forms of damage such as bleeding or flushing of asphalt pavements are not directly integrated. Heavy loads on asphalt surfaces that have been designed for lighter loads may create this type of damage. A loss of skid resistance may result. This may be the byproduct of too much or too soft asphalt utilized for pavements supporting the heavy loads. A seal coat may be applied with an adequate quantity of asphalt to reduce heavy truck damage.
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Hawaii Asphalt Pavement Industry. 2003. Available from: http://www.hawaiiasphalt.com/HAPI/modules/04_pavement_types/04_pavement_types.htm 15 United States Department of Transportation. 1998. Videotapes Explain the How and Why of Laboratory Test for Resilient Modulus. Focus, July/ August. 16 Guide for Design of Pavement Structures, Document Number: AASHTO GDPS-4, American Association of State and Highway Transportation Officials (Jan-1993). 17 Weight Tolerance Permits, Research Report 1323-2F, Texas Transportation Institute, Texas A&M University System and Texas Department of Transportation, 1994.
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Pavement Maintenance and Life Span Highway maintenance and condition are dependent on several variables, including but not limited to: climate, pavement layer thickness, pavement material quality, maintenance, roadbed soil properties, temperature, quantity and weights of axle loads and truck configurations on the pavement.18 Pavements are typically designed for an economic life of 20 years.19 Georgia's highways, for example, are engineered to sustain average traffic over a 20-year period.20 Bridges, however, are typically designed with an economic life of 75 years.21 These life spans pose a challenge for transportation infrastructure facilities to support a specified design load or number of load repetitions. The load characteristics of the anticipated traffic over the targeted useful design life of the structure are needed and not always available. Ideally, quality pavement is designed to last 30 years. However, fatigue may accelerate deterioration and result in earlier replacement. Since traffic volume is heaviest on the highways, and truck traffic continues to increase each year, pavement replacement may often be needed in less than ten years. Pavement fatigue remains the greatest threat to the quality and performance of every road. Pavement Fatigue Historically, highway infrastructure protection has been the primary consideration in determining truck size and weight limits.22 Weights and dimensions of trucks tend to influence the costs that highway agencies must bear to construct and maintain a highway system to serve present traffic and that anticipated in the future. Pavement deterioration accelerates with axle weight, the number of axle loadings, and the spacing within axle groups. The axle loads and spacing on trucks also affect the design and fatigue life of bridges. Truck dimensions influence roadway design -- truck width affects lane widths, trailer or load height affects bridge and other overhead clearances, and length affects intersection and curve design. Truck designs are determined by existing pavement and bridge strength and roadway geometry. Pavement failure is dependent on numerous variables, including but not limited to climate, environmental factors, materials, design, traffic, and usage. Since pavement damage increases with time, it is virtually impossible
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 19 Leidy, J. P., Clyde E. Lee and Robert Harrison. 1995. Measurement and Analysis of Traffic Loads Across the Texas-Mexico Border. Center for Transportation Research, University of Texas at Austin. For Texas Department of Transportation. 20 Performance Audit: Georgia Department of Transportation Permits and Enforcement Program, Performance Audits Operations, Department of Audits, State of Georgia, March 2000. 21 Jooste, F.J., E.G. Fernando, Victoria. Superheavy Load Move: Report on Route Assessment and Pavement Modeling, Cooperative Research Program Research Report 1335-1, Texas Transportation Institute, Texas A&M University System, October 1994. 22 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000.
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to pinpoint any specific illegally overweight truck to quantify its independent contributions to such damages. New construction costs, risks to public safety, and additional design requirements for the infrastructure are all byproducts of pavement fatigue.23 Cracking and/or joint-related problems create rigid pavement failure. This occurs when the tensile stress (from loading, temperature, etc.) exceeds the modulus of rupture.24 In theory, the concrete is expected to have an infinite life if the stress ratio is below 50%. In practice, this may be a challenge. When the stress ratio exceeds 50%, the number of load cycles to failure decreases rapidly. Axle groups, such as tandems or tridems, influence pavement load distribution. According to the Comprehensive Truck Size and Weight Study, these groups allow greater weights to be carried and result in the same or less pavement distress than that occasioned by a single axle at a lower weight.25 Pavement life and performance is also affected by the spread between two consecutive axles. The greater the spacing, the more each axle in a group acts as a single axle. Additionally, the steering axle of a truck can cause significant damage to pavement.26 Some observations show more total deflection under the steering axle than under the trailer axle. This may be due to horizontal offsets of steering tires versus dual trailer tires, tractor suspension system dynamics, and/or consistent static weight (tractor) loading on the steering axle, regardless of vehicle payload. According to the American Concrete Pavement Association, ESALs are defined as the "summation of equivalent 18,000-pound single axle loads used to combine mixed traffic to design traffic for the design period."27 ESALs are sometimes used to compare relative pavement impacts of various truck configurations with different numbers and types of axles.28 Increases in axle load correspond to increases in pavement fatigue. Traffic loadings greatly impact thinner pavements. Traffic loadings, coupled with environmental conditions, especially in places of variable climate, also accelerate the rate of pavement fatigue. Axles are the fixed bar or beam with bearings at its ends on which truck wheels revolve. The DOT reports that the net effect in axle spacing changes on
Preserving Highway Infrastructure Using Weigh-In-Motion (WIM). Dr. A.T. Bergan, Norm Lindgren, Dr. Curtis Berthelot , Bob Woytowich, University of Saskatchewan & International Road Dynamics Inc., November 1998. 24 Kilareski, W.P., "Heavy Vehicle Evaluation for Overload Permits," Rigid and Flexible Pavement Design and Analysis, Unbound Granular Materials, Tire Pressures, Backcalculation, and Design Methods, Transportation Research Record 1227, 1989. 25 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 26 Weight Tolerance Permits, Research Report 1323-2F, Texas Transportation Institute, Texas A&M University System and Texas Department of Transportation, 1994. 27 American Concrete Pavement Association. 2005. http://www.pavement.com/ 28 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000.
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pavement deterioration is complex and highly dependent on pavement structure.29 Tire characteristics vary according to materials, design, and manufacturer, among other variables. Consequently, the accelerated rutting of pavement is sometimes associated with tire characteristics. Wide-base single tires lack strong rut resistance and tend to cause 1.5 times more rutting than dual tires on the flexible pavements. In a laboratory, pavement impacts are observed by applying distresses and strains to different pavement samples. These pavement distresses are standardized to an 8,000pound axle equivalent through use of Load Equivalency Factors (LEF), which can differentiate between distresses, rather than an ESAL. Pavement distresses may include alligator (fatigue) cracking, bleeding, block cracking, corrugation and shoving, depression, joint reflection cracking, longitudinal cracking, patching, polished aggregate, potholes, raveling, rutting, slippage cracking, stripping, transverse (thermal) cracking, and water bleeding and pumping. The reader is referred to the website of Hawaii's Asphalt Pavement Industry in order to view photographs and information concerning each of these forms of pavement distress. 30 Aged asphalt pavements are susceptible to stiffness and brittleness due to an increase in viscosity. This leads to fatigue cracking. Therefore, rheological properties are very important to pavement design and performance. Rutting and bleeding may result from pavements that greatly deform and flow. In Georgia, for example, visible forms of pavement damage caused by overweight vehicles include, but are not limited to, rutting and load cracking.31 Load cracking happens when small pieces of pavement are dislodged from the surface of the road. Rutting occurs through permanent depressions in the pavement along the wheel path of traffic. Pothole development and shoulder damage are hazardous to passenger cars and school buses. Rut development contributes to severe hydroplaning, or wet pavement skidding. This poses a serious risk to drivers because traction is lost when water lifts a tire away from the road. Bridges and the Federal Bridge Formula Bridges were a different story. As urban and rural diverged and the population exploded, numerous bridges were built throughout the U.S. in the 1800s and 1900s. A bridge formula was needed to effectively reduce pavement and structural fatigue on bridges. In the 1940s, AASHTO recommended a bridge formula concept. It was not fully developed until 1962. The Federal-Aid Highway Amendments of 1974 required vehicles to comply with the Federal Bridge Formula (FBF).
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 30 Hawaii Asphalt Pavement Industry. 2003. Available from: http://www.hawaiiasphalt.com/HAPI/modules/04_pavement_types/04_pavement_types.htm 31 Performance Audit: Georgia Department of Transportation Permits and Enforcement Program, Performance Audits Operations, Department of Audits, State of Georgia, March 2000.
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The FBF is now used to preserve our nation's bridges and control vehicle weights. It is a function of the number of axles and axle spacing on a truck. It effectively calculates the maximum allowable weight on any group of axles. Some states, such as Arizona, use the FBF to determine the axle weights for overweight vehicles.32 The Federal Bridge Formula B33 is defined as: W = [LN/N-1 + 12N + 36] where: W = the maximum weight in pounds that can be carried by a group of two or more axles to the nearest 500 pounds L = the distance between the outer axles of the group N = the number of axles in the considered group The FBF is an approximation of the 5% and 30% overstress criteria.34 The National Bridge Inventory is used as a tool for the estimation of different scenario vehicles on a sample of bridges. While criteria vary from agency to agency, deficient bridges require replacement. Cracks develop in materials at points of high stress concentration. Steel bridges and pre-stressed concrete spans, if overloaded, are susceptible to fatigue. A doubling of stress creates an eight-fold increase in steel component damage. The repetitive applications of high stresses, particularly those produced by different motor vehicles, accelerate bridge fatigue. Therefore, the design stresses are far below stresses at which bridge failure occurs. The HS-20 and the H-15 are the most common bridge designs. These designs are based on one of two standard loadings. Heavy truck traffic on interstates and other highways call for the HS-20 bridge design. HS-20 designs typically replace H-15 designs. Lower functional class facilities, where older bridges are concerned, use the H-15 designs. Some states shore up bridges rather than replace them. Others opt for postings to prohibit use by the vehicles that would create the most damage. The cost of strengthening a bridge is a significant portion of the cost to replace the entire structure. Vehicle gross weight, the weight on various groups of axles, the distance between axles, and the type and length of bridge all influence the impact of truck and weight policies on bridges. Such policies significantly affect bridge impacts. Truck length, specifically
Arizona Department of Transportation, Motor Vehicle Division. 2005. Commercial Vehicle Enforcement. Available from: http://www.azdot.gov/mvd/faqs/scripts/faqs.asp?section=cp#4 33 United States Department of Transportation. 2004. Western Uniformity Scenario Analysis: A Regional Truck Size and Weight Scenario Requested by the Western Governors' Association. Washington, DC: United States Department of Transportation. 34 Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000.
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wheelbase, greatly impacts bridge stress for long-span bridges.35 Further studies are now needed on the impacts of heavy trucks on fatigue and bridge deck deterioration. Pavement Costs Pavement costs vary from place to place and from time to time. Pavement costs are dependent on materials, thickness, quantity, and, of course, quality. Geographic and environmental conditions are also considered. The design life of pavements is dependent on these and other variables, including the volume of traffic, frequency of traffic, and the weight of the vehicles. These all take their toll on the life of pavements. Loads create compression and bending of pavements. These lead to rutting and cracking. Heavy axles cause greater and faster pavement fatigue than light axles. For example, a 24,000-pound truck axle consumes over 2,000 times as much pavement life as a 2,000-pound automobile axle.36 The Significance of Fuel Taxes in Arizona and Other U.S. States In order to defray the costs of pavement maintenance and replacement, state and federal taxes on fuels are assessed to drivers. Crude oil costs account for the largest cost of gasoline. Federal and state taxes are the second largest cost of gasoline. The tax on a gallon of diesel fuel is only slightly higher than the tax on gasoline used by most motor vehicles. Fuel taxes appear to shift the tax burden from heavier commercial vehicles to smaller passenger vehicles. Yet, heavy trucks create far greater pavement damage than these other motor vehicles. In fact, some engineers neglect car and light trucks with respect to pavement strength design.37 The fines, fees, and penalties that illegally overweight vehicle drivers face do not appear to be proportional to the pavement fatigue costs they cause. Fuel savings that may result from reduced vehicle travel that results from consolidating cargo into one overloaded trip are offset by highway deterioration and damaged pavement.38 In 1997, approximately $200 million of the revenues generated for the Arizona Highway User Revenue Fund derived from commercial motor carrier taxes. These taxes were based on vehicle miles traveled in Arizona and were monitored through these ports-ofentry.39
Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 36 South Dakota Department of Transportation. 2002. SDOT Briefing: Truck Weights and Highways. 37 Corley-Lay, J. 2005. In "Troopers ticketing more heavy trucks," by Pat Stith. The News & Observer. August 17, 2005. 38 Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987. 39 Norton, D. R, 1997. Performance Audit: Department of Transportation Motor Vehicle Division's Revenue Functions, Report to the Arizona Legislature, Report No. 97-4. Phoenix: State of Arizona Office of the Auditor General. http://www.auditorgen.state.az.us/Reports/State_Agencies/Agencies/Transportation,%20Department%20of /Performance/97-04/97-4.pdf
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In November 2004, the American Petroleum Institute reported that state and federal taxes on diesel fuel amounted to 52.4 cents per gallon plus 1 cent per gallon Underground Storage Tank tax in Arizona.40 This was only slightly higher than the U.S. average of 50.1 cents per gallon. An additional 9 cents per gallon on diesel fuel was also assessed to Arizona vehicles with a gross weight of 26,000 pounds or over. In September 2005, regular grade gasoline was offered at the same price as diesel fuel in some cities in Arizona and across the USA. This was primarily due to a disruption in fuel supplies attributed to Hurricane Katrina.41 This led many to speculate that any major natural or unnatural disaster could spark significant fuel shortages and price inflations. Between 1950 and 2002, the amount of gasoline and diesel usage increased dramatically in Arizona. Consumption increases were 1287% for gasoline and 6550% for diesel. In Arizona, large truck travel was projected to increase by 78% between 2003 and 2010. This is one of the highest rates of increase in the country, following Utah (82%) and Nevada (85%).42 The rise in diesel fuel usage corresponds to a jump in truck traffic and, therefore, higher costs than ever for pavement maintenance and replacement.43 Further spikes in diesel fuel costs may also contribute to an increase in illegally overweight motor carriers as truckers seek to economize and haul heavier cargo. The Congress may be pressured to increase the allowable gross weight and axle weight limits, as it was in 1975 due to the jump in fuel costs. Such legislation would contribute to accelerated pavement fatigue and expenses. Pavement Cost Methods Marginal cost and incremental cost are two economic cost methods used for highway damage cost analysis. Tolliver defines the long run cycle of a highway as the entire time of existence from initial construction to abandonment.44 The addition of one more ESAL to a highway section leads to marginal cost impact analysis. This corresponds to the additional consumption of highway capacity. Incremental costs account for relatively large traffic increases as opposed to a single ESAL analysis.45 Yet, as discussed, highway
American Petroleum Institute. 2004. Policy Analysis and Statistics. "Nationwide and State-by-State Motor Fuel Taxes," November 2004. Available from: http://apiec.api.org/filelibrary/Gas%20tax%20November%202004%20Final.pdf 41 ESRA Consulting Corporation. 2005. Internal report. 42 The Road Information Program. 2004. America's Rolling Warehouses: The impact of increased trucking on economic development, congestion, and traffic safety. http://www.tripnet.org/TruckingReport020904.PDF 43 Arizona Transportation Planning Division. 2003. 2002 Arizona Transportation Factbook: Transportation Relevant Statistical Information. Phoenix: Arizona Department of Transportation. http://tpd.az.gov/reports/pdf/2002factbook.pdf 44 Tolliver, Denver. Highway Impact Assessment. Westport, Connecticut: Quorum Books, 1994. 45 Eriksen, Ken, Kenneth L. Casavant, Impact of Increased International Trade (NAFTA) on Washington Highways, Part II: Highway Impact by Corridor, EWITS Research Report Number 25, Washington State University and US Department of Agriculture, November 1998.
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damage costs fluctuate so these models may not offer the practicality that pavement damage analyses require. In actuality, it is very difficult to assess highway damage costs due to data requirements that most ports and mobile enforcement units lack. Pavement damage is dependent upon many variables and complexities. No equation or model we know of accounts for each of these variables. The few estimates that are available are either outdated or specific to one locality.
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III. IDENTIFICATION OF OVERWEIGHT TRAFFIC Manual and Automated Traffic Counting Techniques Traffic volume is estimated by counting the number of vehicles that pass a point along a highway or street during a specified time period. Traffic detectors automate the counting of passing vehicles. The most common traffic measuring equipment is a pneumatic road tube. Tubes are placed across the road perpendicular to the traffic stream. A counting device is triggered through changes in tube pressure as axles pass over the tube. However, these devices only record axle passage. The data must be converted to vehicles and vehicle classes according to preset axle-spacing parameters. Therefore, some degree of error is anticipated. 46 In contrast, induction loop detectors, which are embedded in the pavement, record the passage of actual vehicles rather than axles. Other sensing equipment includes sonar and radar detectors. However, these devices are generally used for real-time traffic flow monitoring. They are not typically calibrated for traffic counting and classification. According to the ADOT HPMS Data Team, 2002, "raw" traffic counts are conducted with rubber tubes stretched across the road. These must be adjusted to compensate for over-counting by multi-axle vehicles. Traffic classification allows for the development of axle correction factors, which are applied to any raw, tube-based counts. Traffic counts obtained by magnetic induction loops that are permanently imbedded beneath a roadway surface eliminate the need for axle factoring. The presence of a vehicle via a magnetic field is detected by electronic traffic counters connected to "loops." Similarly, wires that are installed in the street at signalized intersections activate signal changes. Such techniques reduce the likelihood of an over-count of vehicles with a lot of axles, such as multi-trailer ("18-wheeler") trucks.47 Tubes or loops are generally used to obtain raw traffic counts. These require seasonal adjustments to compensate for monthly and daily fluctuations of vehicular traffic. Such adjustments are done prior to the quote or publication of any traffic volume information. This adjusting procedure provides a traffic volume that best approximates the use of a given highway section for a typical 24-hour day of the year. Automatic traffic recorders (ATR), a network of continuous traffic recorder stations, produce seasonal adjustment factors. The ADOT Data Section operates 69 ATR stations statewide, which monitor vehicular traffic twenty-four hours each day of the year. These ATR stations are "polled" daily via telemetry and computer software to report the previous day's travel activity. Traffic data polled from ATRs are stored and processed in both monthly and annual
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GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 47 Average Annual Daily Traffic, Arizona Department of Transportation, Transportation Planning Division, Data Team. http://tpd.azdot.gov/datateam/aadtinfo.php
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cycles, which are subsequently applied to raw counts taken on all highway segments that are assigned to a particular set of ATR stations. Once the field crews obtain and report the raw traffic counts, the data are downloaded and stored in a computer. These are later processed and converted to average annual daily traffic volumes (AADT). While it is important to gauge the volume of truck traffic, it is equally imperative to know the weights of the trucks for enforcement and safety purposes. Traditionally, the static scales are in widespread use. However, with the advent of WIM sensors, this technology is gradually supplementing, if not replacing, a lot of scales at ports across the USA. In Arizona, the use of WIM stems from a feasibility study that installed and assessed slow speed Weigh-In-Motion (SWIM) equipment for enforcement applications.48 Weigh-in-motion Sensors WIM devices are commonly used as an alternative to static weigh stations. WIM allows for the effective monitoring of gross vehicle and axle weight monitoring as trucks drive over a sensor. The WIM captures and records the data without requiring the trucks to stop. It provides real-time and accurate counts and gauges compliance with state and federal laws. The WIM scale takes an instantaneous reading of a fluctuating or oscillating force. Since WIM recorders convert signals from the sensors into load values, there is a potential for WIM measurement errors. Dynamic loading errors appear to be dependent on a number of factors including acceleration, braking, road conditions, vehicle speed, and vehicle type. 49 Therefore, the recorders must be recalibrated frequently.50 WIM Systems are classified according to Type I, II, III, or IV according to application through American Society for Testing and Materials (ASTM) Designation E 1318-94.51 These vary according to user requirements and performance. Different data gathering capabilities, speed ranges, and uses define the four different WIM systems.52 There are three types of sensors commonly used in WIM Systems. These include the bending-plate sensors, piezoelectric sensors, and single load cell scale. The bending48
Castle Rock Consultants. 1989. Port of Entry Weigh-In-Motion Feasibility Study. FHWA-AZ89-702. Phoenix, Arizona: Arizona Department of Transportation. 49 Oregon Department of Transportation Research Unit, Policy and Research Section, Transportation Development Branch, Oregon Department of Transportation. 1998. Port-of-Entry Advanced Sorting System (PASS) Operational Test. FHWA-OR-RD-99-15. 50 GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 51 American Society for Testing and Materials. 1994. Standard Specification for Highway Weigh-inMotion (WIM) Systems with User Requirements and Test Method. ASTM Committee E-17 on VehiclePavement Systems. ASTM Designation E 1318-94. 52 McCall, B. and W. C. Vodrazka. 1997. State's Successful Practices Weigh-In-Motion Handbook. Washington, DC: Department of Transportation Federal Highway Administration.
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plate sensors consist of steel plates embedded in concrete pavement. The plate deflects in an amount proportional to the load when a vehicle passes over the plate. The amount of deflection is transmitted to a data recorder. The load is computed. Bending plate sensors are believed to be more durable and accurate than piezoelectric sensors. Piezoelectric sensors, contrastingly, consist of a casing containing a piezoelectric material. This generates an electrical charge when subjected to mechanical stress. The vehicle load creates a charge that is proportional to the stress it produces. Piezoelectric sensors are an economical alternative to bending-plate sensors and can be moved from location to location. The Single Load Cell Scale constitutes a single hydraulic load cell installed at the center of each platform to measure the force applied to the scale. When properly installed and calibrated, Single Load Cell WIM systems are expected to provide gross vehicle weights that are within 6% of the actual vehicle weight for 95% of the trucks measured.53 Road conditions, road geometry, and vehicle condition impact WIM system performance. Vehicle dynamics also affect the accuracy level of the WIM systems. Accuracy is therefore lower than that for a static scale used for enforcement weighing. No absolute accuracy for a WIM scale exists. Therefore, any WIM accuracy is always quoted as a percentage accuracy with a confidence level. The confidence level is generally set at either 68% or 95%. ASTM accuracy uses the 95% level, which means that we can be 95% confident that the actual weight is within the measured WIM stated range.54 At weigh stations, Automatic Vehicle Identification devices may check registration and safety data. Since axle or truck weights are not identifiable by this technology, Strathman and Theisen also suggest the use of WIM.55 Automatic Vehicle Identification devices, used in combination with WIM technology, may offer cost-effective enforcement options. Traffic Data Collection Methods in Arizona A recent study conducted by the ADOT documents discrepancies in data collection and equipment.56 ADOT collects and maintains traffic volumes for all highways at specific collection sites. Some sites record traffic volumes continuously throughout the year, but most sites are only counted for 48 hours once a year. The results of the collection effort are used to compile or compute AADT values for every section of the state highway system.
Weigh In Motion Technology - Economics and Performance. Rob Bushman, Andrew J. Pratt. Presented at NATMEC '98, Charlotte, North Carolina, 1998. 54 Ibid. 55 Strathman, J. G. and G. Theisen. 2002. Weight Enforcement and Evasion: Oregon Case Study. FHWAOR-DF-02-12. Salem, Oregon: Oregon Department of Transportation. 56 GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation.
53
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AADT is the average 24-hour traffic volume at a given location over a full 365-day year. Therefore, the AADT at a given site is calculated by dividing the total number of vehicles passing a site in a year by 365. About 70 collection sites are equipped with ATRs, which record traffic continuously throughout the year. For sites at which a 48-hour count is used, the site AADT is estimated by factoring the 48-hour count by seasonal, monthly, and day-of-week adjustments.57 ADOT uses several types of technology for automated traffic counting. Automatic traffic recorders (usually inductive loop detectors) are primarily used at the continuous monitoring sites, and pneumatic tube detectors for short-term counts. The ATR data are used to determine seasonal adjustments to short-term counts. Some of the ATR sites also record vehicle classification and weight. Specific sites are established for the collection of vehicle classification data. These sections are assumed to represent all highway sections within a specified area. Data collection at these sites is shared between the Long Term Pavement Performance (LTPP) program at the Arizona Transportation Research Center, and the Transportation Planning Data Team.58 ADOT performs manual vehicle classification counts at a few sites. Manual counts are performed over 6-hour intervals. In other locations, traffic counting devices are used to conduct 48-hour counts. These devices convert axle observations and measurements to vehicle classes, based on assumptions programmed into the recording devices. Finally, several sites are equipped with continuous automatic vehicle classification (AVC) devices that function in the same manner as the ATR equipment. All AVC sites use axle sensors and induction loops for vehicle detection and classification.59 The MVD, the ADOT Materials Group, and the Arizona Transportation Research Center (ATRC) all collect vehicle weight data for Arizona highways. MVD collects truck weights for enforcement purposes, while the Materials Group and the ATRC collect vehicle weight measurements for pavement management and research. The MVD uses static scales at port-of-entry (POE) locations statewide to measure gross vehicle weight and axle loads. While these scales have the benefit of a high degree of accuracy, static scales are insufficient for the measurement of a large volume of traffic. POE stations do not have the technical resources for truck weight data collection and storage, as the enforcement operations only require weight data for an inspection in progress. Weight records are recorded only at stations with WIM sensors, and these data are only maintained on the WIM recorder for a 24-hour period. 60 ADOT is currently in the midst of implementing the Data Collection Project. The Data Collection Project entails collecting vehicle counts and weights at selected MVD sites on a 24 hours-a-day, 7-days-a-week basis. ADOT is also striving to include all data
57
GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 58 Ibid. 59 Ibid. 60 Ibid.
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collection devices into a combined database in order to provide a better picture of where and when the heavy trucks are running. These data and information will be used to deploy our mobile operations at those locations identified as routes that overweight vehicles most frequently use. This should also help reduce circumvention of fixed POE sites. The Data Team and ATRC use WIM sensors to record weight measurements for vehicles traveling at highway speeds. ADOT uses two types of WIM sensors for these applications: bending plates and piezoelectric cables. However, these sensors are not always operational. ADOT Transportation Technology Group staff report that approximately 50% of the Freeway Monitoring System traffic sensors function at a given time. According to the Data Team, about 90% of the ATRs used to collect data for the HPMS fail at least once per year. A recent study shows that, on a given day, only 74% of the ATRs (55 out of 74) transmitted any data.61 Not every port in Arizona uses WIM technology. WIM sensors may only be present in one of two lanes of traffic. The lack of WIM sensors means that many overweight vehicles will not be detected. This will result in uncompensated costs due to pavement damage induced by overweight vehicles that are not weighed, monitored, or cited for infractions.62 On the other hand, according to interviews with ADOT staff, the WIM sensors are not particularly effective for capturing vehicle weight data. Certain bending-plate installations are only operational for a 3-month period before being rendered unusable due to excessive traffic loading. Hence there is a dire need for not only improved technologies, but also a calculation that will account for the data collection discrepancies that exist within agencies, highways, and elsewhere.
GIS/Trans. Ltd., Lima and Associates, and Transportation Research and Analysis, Inc. 2001. Enhancing Arizona Department of Transportation's Traffic Data Resource. Final Report 492. Phoenix: Arizona Department of Transportation. 62 Ernzen, J. M. 2005, J. M. 2005. Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
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IV. SURVEY OF TRANSPORTATION OFFICIALS AND/OR TRUCK ENFORCEMENT PERSONNEL FROM SEVERAL U.S. STATES AND CANADA Introduction ESRA developed a survey to ascertain the state-of-the-practice of current mobile enforcement activities across the nation. Questionnaires were faxed, e-mailed, and/or queried by telephone to the directors and public safety officials of all 50 U.S. states and the ten provinces and three territories of Canada from January to April 2005. Some officials were telephoned for follow-up interviews. Responses were received from 25 states: Alabama, Indiana, Oregon, Alaska, Louisiana, Tennessee, Arizona, Maryland, Texas, Arkansas, Missouri, Utah, California, Montana, Vermont, Colorado, Nebraska, Washington, and Delaware, North Dakota, Wisconsin. Georgia, Ohio, Illinois, Oklahoma, Two responses were obtained from Canada: The Province of Nova Scotia and The Territory of Nunavut. Not all respondents from the U.S. and Canada answered all the questions on the survey. The majority of data requested was either undetermined or unavailable due to funding or staffing issues. Many respondents indicated that tasks were divided among different agencies. The information for South Dakota was acquired from "SDOT Briefing: Truck Weights and Highways." Additional information on Arizona Ports of Entry was obtained through "Arizona Ports of Entry: Arizona Department of Transportation JLBC/OSPB Joint SPAR Report," 2000 Strategic Program Area Review. It was then reported that there were "....13 ports, 9 mobile stations, 142 officers, and a Phoenix Central Permits office which only issues permits" under the auspices of ADOT-MVD.63 By 2005, Ernzen reported that there were 21 fixed ports of entry in the State, six of which were located on the Arizona-Mexico border.64 Our aim was to review and learn about the policies and practices of other agencies and bureaus in order to quantify and, ultimately, reduce pavement damage associated with overweight vehicles. Clearly, there is a dire need for improved mobile enforcement units, equipment, and data collection "across the board," in all U.S. states. Arizona is a state that merits further
Arizona Department of Transportation. 1999. Arizona Ports of Entry: Arizona Department of Transportation JLBC/OSPB Joint SPAR Report, 2000 Strategic Program Area Review (available from: http://www.azleg.state.az.us/jlbc/ports.pdf) 64 Ernzen, J. M. 2005, J. M. 2005. Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
63
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attention due to its border with Mexico. As our survey demonstrates, geography, economy, industry, and climate appear to influence the number of violations by overweight vehicles in most U.S. states. For example, in Georgia, there are numerous overweight vehicles associated with the wood industry. In Indiana, these overweight vehicles may be linked to quarries and construction activities. Overweight vehicles create costly damage to roads and structures. Some violators know the schedule of the mobile enforcement units and strategically violate the weight limits after hours of operation. Other violations occur during operating hours in daylight. Survey Responses Question #1 1. What is the measured or estimated percentage of travel in your state that is comprised of vehicles exceeding legal limits (gross or axle or both) on weight? __________ (If there is a report, memo, or other document, can you send us a copy?) Table 1. Measured or estimated percentage of in-state travel comprised of vehicles exceeding legal limits (gross or axle or both) on weight STATE Arizona Delaware* Indiana* Louisiana Montana Nebraska Oregon South Dakota Utah Washington Wisconsin Alaska, Colorado, Georgia, Illinois, Maryland, Missouri, North Dakota, Ohio, Oklahoma, Tennessee, Vermont * varies by route PERCENTAGE 30 ~5 ? 20 <2; 3-5 2 6.9 <0.5 10 0.5 <10 <5 7 Unknown
Only 11 states provided estimates of the percentage of trucks that were operating in excess of legal weight limits. Arizona's estimate of 30% is by far the highest. Most of the other states perceive the overweight vehicle traffic to amount to less than 10% of the trucks operating on their roadways.
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Question #2 2. Have you estimated a cost in terms of damage to pavements, structures, or safety due to these overweight vehicles?
Yes No
If "yes" what are these costs? ___$________________________________________ (If there is a report, memo, or other documents, can you send us a copy?) Table 2. Estimated cost of overweight vehicle damage STATE Indiana Maryland Montana South Dakota Vermont Alaska, Arizona, Arkansas, Colorado, Delaware, Georgia, Illinois, Louisiana, Missouri, Nebraska, North Dakota, Ohio, Oklahoma, Oregon, Tennessee, Utah, Washington, Wisconsin ESTIMATED COST OF DAMAGE Rural- $1 million per lane per mile Urban- over $1 million per mile due to property costs. $36 million per year due to overweight dump trucks $700,000 more than $1.1 million in six county bridge replacements in the last 2 years. > $1,000,000 Not estimated
Only four states have attempted to estimate the damage caused by overweight vehicles. The quality of these estimates is undetermined. Indiana's seems implausibly high. For that state Interstate Highway system alone, the cost would be in the $3.5 billion range. This is $2 billion more than Indiana spends per year for ALL state highway expenses. At the other extreme, Montana's estimate seems implausibly low given the state's $500 million annual expenditure on state highways. Maryland's estimate is focused on dump trucks. This partial information cannot be extrapolated to other classes of vehicle. South Dakota's data is limited to the impacts on six specific bridges. Vermont's estimate of over a million dollars in damage is a safe statement, but too imprecise to be of much use. The paucity of good information on this issue is truly disappointing. The importance of having good information is emphasized by ADOT's Intermodal Transportation Division projection that a 10% jump in overweight vehicles could cause a
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$20 million annual increase in costs associated with road repair and maintenance.65 Roads designed for life spans of 20 years may fall short of that without adequate weight enforcement. Question #3 3. Have you done any studies of overweight vehicles in response to proposals to change the weight limits? If so, can you summarize the outcome of that/those studies? (If there is a report, memo, or other document, can you send us a copy?) Only eight states professed to have conducted studies of overweight vehicles: Colorado, Georgia, Indiana, Louisiana, Missouri, Montana, North Dakota, and Washington. None of these studies specifically linked weight to pavement damage in any scientifically quantified way. Some technical reports are either unpublished or based on studies performed by other U.S. states. For example, Colorado, like Minnesota, considers increasing weight limits during the winter months. However, the various frost depths in Colorado reveal that increasing weight loads during frozen periods is not possible. In order to increase weights on state roads in Georgia, bills are introduced each year when legislature is in session. In Missouri, studies exist on the impacts of increased legal weights on bridges, as proposed by legislation. In Washington, requests are routinely received "...to increase axle loads for `specialty' vehicles (i.e., cement trucks, refuse haulers, emergency response equipment, etc.)." The Washington Department of Transportation uses their layered elastic program (Everstress) to analyze such pavements and to estimate the damages caused by axle load increases through increases in required asphalt thicknesses. These studies, performed by the HQ Materials Pavement Division and the Commercial Vehicle Services branch of the Washington Department of Transportation indicate that the state is successful in its enforcement of axle weight and weight per inch of tire requirements. Indiana intends to enforce existing weight limit laws and utilize virtual weigh stations rather than modify weight limits. In South Dakota, illegal haulers who violate weight limits are pursued through enforcement and prosecution methods. Other states, such as Texas, do not currently have initiatives to change the weight limits, reported at Gross: 80,000 lbs.; Tandem Axle: 34,000 lbs.; Single Axle: 20,000 lbs.
65
Arizona Ports of Entry: Arizona Department of Transportation JLBC/OSPB Joint SPAR Report, 2000 Strategic Program Area Review (available from: http://www.azleg.state.az.us/jlbc/ports.pdf
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Question #4 4. What percentage of the total of trucks on your roads is weighed at your ports-of-entry? ___________________________________________________ Table 3. Percentage of trucks on roads weighed at ports-of-entry STATE Alaska Arizona Georgia Illinois Indiana Louisiana Montana Ohio Oklahoma Oregon Utah Wisconsin Arkansas, California, Colorado, Missouri, Tennessee, Vermont Delaware, Maryland, North Dakota, Texas PERCENTAGE 5.2% 98% 70% 40% 100% weighed on WIM 15% 17.86% 3% 5 to 10% 35%-55% 35-40% 68.7% unknown Not applicable (No state port-of-entry)
Given that ports-of-entry deal with interstate traffic and are not always open, the lower percentages reported here seem more plausible. The higher percentage estimates may represent the ratio of vehicles stopped at the POEs that actually are weighed. Some may not be weighed for efficiency reasons. For example, a flatbed truck without a load is obviously not overweight and may not need to be weighed. Some may not be weighed due to the queue length. If the queue stretches beyond the ramp's storage capacity it would constitute a safety hazard. Trucks arriving when there is no space on the ramp may be waived through the POE without stopping. Some states, such as Oregon, report the use of PrePass. PrePass is an automatic vehicle identification (AVI) system that allows participating transponder equipped commercial vehicles to bypass designated weigh stations, port-of-entry facilities, and agricultural interdiction facilities. Cleared vehicles may proceed at highway speed, eliminating the need to stop.66 While seemingly useful, this system seems to have some limitations. PrePass may check the safety credentials of the driver yet not weigh the vehicle. Vermont performs weight enforcement activities through use of Platform, portable wheel
66
http://www.prepass.com/aboutprepass.htm
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weigh loaders, Semi-portable scales, and WIMs. In Missouri, fixed sites, HSWIMSPrePass, portable scales, and RampWIMs are used to weigh millions of vehicles per year. At the Texas-Mexico border, there are eight ports-of-entry. All trucks entering Texas from Mexico pass over weigh-in-motion scales at these ports-of-entry. Vehicles that fail the weigh-in-motion are weighed on a static scale. Question #5 5. Please indicate typical hours of operation for your ports-of-entry: ________hours Table 4. Typical hours of operation for ports-of-entry STATE Alaska Arizona HOURS 24-hour shifts "Depends on POE (Port of Entry). A large Interstate POE is supposed to operate 7 days a week, 24 hours a day. A smaller secondary POE might be 16 hours 5 to 7 days a week according to traffic and/or staffing. Some are 8 hours five days a week. International POEs hours of operation are determined by Customs agency." 24-hour shifts 24-hour shifts 24-hour shifts 2- 8 hour shifts 16-hour shifts 8-hour shifts 24-hour shifts Not Applicable 18- 24 hours 8-24 hours Not Applicable 8-hour shifts 8-hour shifts 18- 24 hours 24-hour shifts 18-hour shifts 20- 24 hours 12-hour shifts 16-hour shifts
Arkansas California Delaware Georgia Illinois Indiana Louisiana Maryland Missouri Montana North Dakota Ohio Oklahoma Oregon Tennessee Texas Utah Vermont Wisconsin
While several states maintain round-the-clock operation of their POEs, most do not. Drivers of overweight vehicles aware of the closing times of POEs not operating 24 hours a day may time their trips to ensure bypassing a closed POE.
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For example, the eight ports-of-entry in Texas "...operate at varying hours from 6AM to Midnight on weekdays." These ports are managed on the same schedule as the U.S. Customs & Border Protection ports-of-entry. In Oklahoma, "Hours of operation are selectively expanded in response to a need for increased enforcement...from keeping weigh stations open longer hours, varying the hours at specific weigh stations, or double shifts for all stations in January to check registration. The Corporation Commission is facing the same budgetary constraints as ODOT. All of the agencies involved in weight enforcement are working together to maximize available resources."
Not applicable 10%
Varies according to Port-of-entry 13%
2- 8 hour shifts 5%
24-ho ur shifts 28%
8-ho ur shifts 14%
12-ho ur shifts 5%
18- 24 shifts 10%
16-ho ur shifts 10% 18-ho ur shifts 5%
Figure 1. Typical hours of operation for ports-of-entry in selected states
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According to Vermont, "Sixty percent of DMV enforcement activity is spent on state initiatives i.e. size, weight, IFTA (International Fuel Tax Agreement), IRP (International Registration Plan), dyed fuel etc. and the other forty percent is MCSAP (Motor Carrier Safety Assistance Program) enforcement activities in which weight enforcement can be part of a MCSAP inspection. Most officers, based on national statistical violation trends, work Monday ? Friday between the hours of 0600-1800 hours. Inspectors may work outside of that time frame but the bulk of our activity is during the listed days and time." In Arizona, the hours of operation vary from port-of-entry to port-of-entry. "A large Interstate POE is supposed to operate 7 days a week, 24 hours a day. A smaller secondary POE might be 16 hours 5 to 7 days a week according to traffic and/or staffing. Some are 8 hours five days a week. International POES hours of operation are determined by the Customs agency." Unsurprisingly, the respondents with limited hours of ports-of-entry operation expressed interest in extending hours of operation. However, budget and staffing issues prevented such activities. Nowhere was this more evident than in Arizona, where, since 1998, truck traffic increased significantly while the hours of operation at Arizona ports were cut by 39%.67
67
Ernzen, J. M. 2005, J. M. 2005. Port Runners ? Impacts and Solutions. FHWA-AZ-05- 563. Phoenix, Arizona: Arizona Department of Transportation.
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Question #6 6. For your mobile enforcement units on a statewide annual basis, typically: a. How much is budgeted for this effort? _________________________________ b. How many person-hours are assigned to this duty? _______________________ c. How many vehicles are weighed? ____________________________________ d. What percentage of the weighed vehicles exceeds the legal limits? __________ e. How many pounds (lbs.) over the legal limit do overweight vehicles average? __________________________________________________________ Table 5. Amount budgeted for mobile enforcement units on an annual basis STATE Alaska Arizona Arkansas California Colorado Delaware Georgia Illinois Louisiana Maryland Missouri Montana North Dakota Oklahoma Texas Utah Vermont Indiana, Oregon, Tennessee, Wisconsin MOBILE ENFORCEMENT BUDGET $600,000 "$5.8 million total personnel costs, facilities" $12,213,614 "$88,922,000 for commercial vehicle inspection and enforcement." $1.6 million $675,000 $18,973,729 $400,000 $2,227,072 "cost absorbed in overall budget of approximately $12 million per year" "$1,527,812 (vehicles, fuel, maintenance and salaries)" "$712,340 expended" $90,000 ~ $2,500,000 "State Funding: $27,008,917; Federal Funding: $24,170,994 (POE Operations)" $500,000- $700,000 $748,690 unknown
The amount budgeted for mobile enforcement units on a statewide annual basis vary from state to state. Since some figures reached into the tens of millions of dollars, it was assumed that these respondents indicated the overall budget amounts rather than their mobile enforcement unit budgets. Such mobile enforcement unit costs were typically absorbed into the overall budgets. For example, as shown in Table 5, in California, the amounts reported were $88,922,000 (for commercial vehicle inspection and
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enforcement); and in Texas, $51,179,911 (for state and federal funding). Of this Texas budget, $24,170,994 was earmarked for ports-of-entries. This study determined that, among all respondents who reported specifically their mobile enforcement unit budgets, the average amount budgeted for mobile enforcement units in these states was approximately $3.7 million. In Arizona, the mobile enforcement budget was estimated at $5.8 million for total personnel costs and facilities. The budget in North Dakota was lowest at $90,000. In Tennessee, a merger between the Commercial Vehicles Enforcement unit and the Highway Patrol recently occurred through the Department of Safety. It was reported that troopers were assigned to either road patrol or fixed inspection stations. The troopers were not assigned to a set number of hours per day of mobile weight enforcement. A lack of calibrated and certified portable wheel weighers resulted in very few trucks being weighed. Therefore, no budgets or statistics we requested were available at the time this questionnaire was issued. Approximately $600,000 is budgeted yearly in Nova Scotia for mobile enforcement units. This is about the same amount budgeted in Alaska and slightly less than the amount budgeted in Delaware. In Figure 2, the amount of person-hours assigned to the duty of mobile enforcement units on a statewide annual basis in responding states is presented. This amount is dependent on location, need, funding, and staffing operations. Approximately 23% of the U.S. respondents report 2,000- 9,999 hours annually. There are 21,500 person-hours assigned to mobile enforcement unit duties in Nova Scotia.
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Amount of person-hours assigned:
100,000- 450,000 hours 10%
60,000- 99,999 hours 10%
Unknown 28%
26,000- 55,999 hours 10%
10,000- 25,999 hours 19%
2,000- 9,999 hours 23%
Figure 2. Amount of person-hours assigned to the duty of mobile enforcement units on a statewide annual basis in selected states
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Table 6. Amount of mobile enforcement unit person-hours on an annual basis STATE Alaska Arkansas California Colorado Delaware Illinois Louisiana Maryland Missouri Montana North Dakota Oklahoma Oregon Texas Utah Vermont Arizona, Georgia, Ohio, Tennessee, Wisconsin MOBILE ENFORCEMENT PERSON-HOURS* 21,450 3,224 413,504 54,000 8,320 249,600 62,400 40,000 139,776 25,000 5,000 79,000 2,000 2,080 18,720 16,000 Unknown
*lower numbers of person-hours may be per person rather than total numbers of mobile enforcement unit person-hours.
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Table 7. Quantity of vehicles weighed by mobile enforcement units/year STATE California Alaska Arizona Arkansas Colorado Delaware Georgia Illinois Maryland Missouri Montana North Dakota Oregon Texas Utah Vermont Wisconsin Indiana, Oklahoma, Tennessee QUANTITY OF VEHICLES WEIGHED 16,226,790 (includes portable scales: 458; Fixed scales: 11,61,670; WIM 4,264,662 ) 3,495 4,575,085 4,532 51,698 "The annual target is 650 vehicles for portable weigh pads." 10,444,582 ~45,000 ~25,000 3,666 6,358 1,100 ~7,500 881,948 (includes Fixed Scales: 292,053; Semi-Portable Scales: 36,605; Portable Scales: 15,225; WIM: 538,065) 5,400,000 23,732 1,090 unknown
Table 7 shows that Wisconsin (1,090) and North Dakota (1,100) weigh the fewest vehicles. Georgia (10,444,582), Utah (5,400,000), and Arizona (4,575,085) weigh the most vehicles each year. Portable scales account for weighing 650 vehicles in Delaware and 458 vehicles in California. In Texas, a total of 881,948 vehicles are weighed through use of fixed scales (292,053), semi-portable scales (36,605), portable scales (15,225), and WIM (538,065). There are 4,600 vehicles weighed each year in Nova Scotia, Canada. The large variation may be due to errors. Some respondents may have included total quantity of vehicles weighed by both static and mobile enforcement crews. California officials, for example, provide a complete breakdown of the quantities and techniques of vehicles weighed.
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Table 8. Percentage of weighed vehicles exceeding legal limits through mobile enforcement units STATE Alaska Arizona Arkansas Colorado Illinois Louisiana Maryland Montana North Dakota Oregon Texas Utah Wisconsin Delaware, Georgia, Indiana, Missouri, Ohio, Oklahoma, Tennessee, Vermont WEIGHED VEHICLES EXCEEDING LEGAL LIMITS 0.23% 0.53% 0.29% 12% ~27.1% ~25% 1.4% 10.33% 50% ~5% 3 to 4% 2-3% "nearly 100%" unknown
The overweight violation percentages range from tiny to nearly 100%. It seems likely that high percentages reflect targeted enforcement. That is, only those vehicles suspected of being overweight are pulled aside by these states' mobile enforcement units. For example, the North Dakota Highway Patrol weighs only 1,100 vehicles per year on a very small annual budget of less than $90,000. However, the mobile enforcement units report that the overweight vehicles are, on average, 3,000 to 8,000 lbs. overweight.
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Table 9. Average estimated number of pounds (lbs.) over the legal limit as reported by mobile enforcement units STATE Utah Wisconsin Illinois Montana Alaska North Dakota Oregon Texas Arizona, Arkansas. Colorado, Delaware, Indiana, Maryland, Missouri, Ohio, Tennessee, Vermont AVERAGE NUMBER OF POUNDS (LBS.) THAT WEIGHED VEHICLES EXCEED LEGAL LIMITS 10,000 6,500 "6,000 over" 4,500 4,000 3,000-8,000 "For calendar year 2004 the overall average violation was 2,278 pounds." "Data is not available; but usually exceeds the weight allowance by a minimum of 1,000 lbs. before enforcement action is initiated." unknown
While most respondents were unable to provide us with this data, such data as are available may be useful to know in order to improve mobile enforcement activities and reduce pavement damage from overweight vehicles. The Iqaluit office of Nunavut, Canada is equipped with a portable weigh-scale that was used to monitor a situation, several years ago, where overloaded rock-trucks were in frequent operation. Now, the Government of Nunavut reports, the scale is rarely needed and used. In Nova Scotia, Canada, mobile weighers are increased in order to reduce the damage caused by overweight vehicles. Question #7 7. What other actions (if any) does your state take to try to reduce the damage caused by overweight vehicles? (If there is a report, memo, or other documents, can you send us a copy?) ____________________________________________
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Table 10. Some actions taken by state officials to reduce pavement damage
STATE Alaska Arkansas California Colorado Georgia Illinois Indiana Louisiana Maryland Missouri ACTIONS "....increased roadside inspections and portable scale weighings..." "The development of virtual weigh stations on secondary bypasses. This study will not end until June 2006. No statistics have been gathered at this time." "Weigh more vehicles, construct more port of entry inspection facilities, relocate and upgrade certain platform scales at inspection facilities." "Vehicle/load combinations in excess of 100 tons are sent to CDOT's Staff Bridge for further analysis and bridge impact." "Have mobile teams off the main interstates and have semi-portable weighing operations at wood mills." "Keep weigh stations open as much as possible." "...educational initiatives to educate the public; judicial outreach program to educate attorneys, prosecutors in representing the state..." "Many overweight loads are routed by our Oversize/Overweight Permit Office personnel to reduce their impact on roads and bridges." "Issue oversize/ overweight permits." "We use the routine overweight permitting process for weights between 80,000# and 152,000#. For these loads and configurations we compare the proposed move to the capacity of the bridges using "envelope" vehicles. For weights greater than 152,000# and non-routine configurations (i.e., superloads) we do an individual bridge analysis (load rating) for all structures crossed along the route by the proposed vehicle. By having these processes, we ensure that the structures are safe to cross along with helping to protect our bridges from sustaining damage during the move. Also, we will load post bridges that do not have the capacity to carry legal loads." "....Planning & Research Division is investigating semi-active vibration absorber technology with regard to bridges. Oklahoma is also working toward automating Oversize/Overweight permitting..." "We computerize scale data and track company weight violation rates. If a company with above average violation rates is based in or has a terminal in Oregon, we contact the company and set up training classes to educate and gain voluntary compliance." stringent penalties and enforcement "We attempt to deploy what certified portable wheel weighers that we do have in traditionally known areas of violations." "Overweight penalties were recently increased for repeat violators." "Departmental action, civil; occasional spring load restrictions." "Enact spring weight restriction period. Suspend or limit use of overweight permits. Post sections of poor roads." Not specified
Oklahoma Oregon
South Dakota Tennessee Texas Utah Wisconsin Arizona, Delaware, Montana, North Dakota, Ohio, Vermont
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The actions taken to reduce overweight vehicle damage are presented in Table 10. Georgia maintains mobile teams off the main interstates and has semi-portable weighing operations at wood mills. Indiana offers a judicial outreach program to educate attorneys in representing the state. Tennessee targets traditionally known areas of violations with the deployment of certified portable wheel weighers. South Dakota issues stringent penalties and enforcement. Louisiana routes overweight loads through its Oversize/overweight Permit Office personnel to reduce their impact on roads and bridges. Texas increases overweight penalties for repeat violators. Oklahoma investigates semiactive vibration absorber technology with respect to bridges. Oklahoma also plans to automate OS/OW permitting. Colorado sends vehicle/load combinations in excess of 100 tons "...to CDOT's Staff Bridge for further analysis and bridge impact." Oregon computerizes scale data to track company weight violation rates. In an effort to gain compliance, companies within Oregon that demonstrate "above average violation rates" are educated through training classes. Question #8 8. What are the actions you would like to take, but are prevented from taking due to financial or other impediments? ________________________________________ Table 11. Summaries of desired actions that are unfunded due to financial and other impediments DESIRED ACTIONS* Additional personnel and equipment Attract and retain qualified enforcement employees through an improved pay plan. Charge more for overweight permits; equivalent to damage done to pavement. Extend hours of weigh station operations. Extend spring weight restriction period. Increase fines/ civil penalties/ weight operations. Increase statewide activities Installation of virtual weigh stations. Installation of Weigh in Motion and/ or portable weigh stations at additional statewide locations. lengthen scale decks and repave more scale ramps re-certify and deploy our portable wheel weighers Transmit WIM data through wireless technology Unspecified * Some states provided more than one response. STATES Indiana, Louisiana, Maryland, Utah Montana Wisconsin Illinois, North Dakota Wisconsin Colorado, Georgia, Wisconsin Alaska, Georgia Arkansas Arkansas, Montana, Tennessee Oregon Tennessee Vermont Arizona, Delaware, Ohio
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In Table 11, the respondents reveal a wish-list of unfunded yet desirable actions. For example, Vermont currently uses WIM stations for screening. However, inspectors "....must physically open the box and boot up the work station monitor in order to observe real time vehicle weights." Therefore, an update of the VDOT WIM stations is necessary for inspectors to monitor roadside traffic from laptops that use wireless technology. According to an official in Oregon: "All of the 91 Oregon DOT scales use 16' decks. We are seeing more and more trailers today with 4 and greater axle groups with air suspension and 18 ? 20 foot spreads. .... when we attempt to weigh the axle groups by splitting them and weighing in two groups, the air suspensions move air and change the weights. We are lengthening scale decks at seven of our interstate scales that frequently weigh these vehicles. By being able to weigh the entire group at once, the weight will be absolutely accurate. As the infrastructure ages, the costs to repave or maintain scale ramps are high. While, in the ideal, I wish had more money to repave more scale ramps, but we are holding our own." Some states, such as Louisiana, note the need for improved technologies at weigh station bypass routes and the construction of new weigh stations at key locations. Some logistical obstacles seem to exist with mobile weight enforcement operations now under the auspices of the State Police rather than the Department of Transportation. In Nova Scotia, Canada, like most U.S. states, there exists a need for additional vehicles and personnel.
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Question #9 9. Where do most of your weight violations occur? Please check all that apply: Vehicles traveling interstate Vehicles traveling intrastate Vehicles traveling across the US/Mexico Border (if applicable) Vehicles traveling across the US/Canada Border (if applicable) Table 12. The locations where most weight violations occur LOCATION OF MOST WEIGHT VIOLATIONS Intrastate Interstate and Intrastate Interstate STATE Alaska, Arizona, Colorado. North Dakota, Ohio, Oklahoma, Vermont, Utah, Wisconsin Arkansas, Illinois, Maryland, Montana Georgia, Louisiana, Missouri, Tennessee California, Delaware Indiana Oregon
Unknown "Borman, I-80/ I-94" "We do not track the interstate versus intrastate status of loads cited for weight violations. Most of the violations we discover are on the interstate highways because that is where we weigh the most trucks. However, you cannot jump to the conclusion they are interstate loads. The better question is where is the highest violation rates? They are at the scales on the lesser traveled highways where trucks operators are not used to seeing more truck weighing effort." Interstate, Intrastate, and U.S./ Texas Mexico Border
While these responses are not conclusive, the relatively higher preponderance of intrastate being seen as the more likely traffic to run overweight would indicate that POEs would be ineffectual in stemming violations by these vehicles. This would tend to argue for either more internal weigh stations or a more active mobile enforcement effort (or both).
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Question # 10 10. When do most of your weight violations occur? _______________________ Table 13. Time when most weight violations occur TIME 6 AM ? 8 PM 6 AM ?12 midnight After hours Between 12-4 P.M. Daylight and early evening Daytime During the construction and harvest seasons No specific time or pattern Spring and fall When weigh stations are open Unknown STATE Colorado Texas Indiana, Oklahoma Montana Louisiana Delaware, Georgia, Ohio, Oregon, Vermont North Dakota Alaska, Illinois, North Dakota, Utah Wisconsin Georgia Arizona, Arkansas, California, Maryland, Missouri, Tennessee
There is not enough consistency in the responses to suggest any useful timing of countermeasures. Anecdotal evidence suggests that knowing violators are likely to try to avoid getting weighed. This would support an "after hours" perception of when most violators are operating. Daytime responses probably reflect the fact that citations are only written when enforcement officers are working, which are during daylight hours. For example, survey respondents in Oklahoma replied: "We do know that truckers frequently gather at rest areas ahead of a weigh station and wait for the station to close for the day (generally around 2 to 3 pm)."
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Question #11 11. Which classes of vehicle have the highest rate of overweight violations in your state? (Please specify number of axles.) _________________________ Table 14. Classes and number of axles of vehicles that have the highest rate of instate overweight violations STATE Alaska Arizona Arkansas Colorado Delaware Illinois Indiana Louisiana Maryland Montana North Dakota Oklahoma Oregon Texas Utah Vermont Wisconsin California, Georgia, Missouri, Ohio, Tennessee * depends on geographic area CLASS AND/OR TYPE OF VEHICLES Class 9 (3S3s__single trailer) 18-wheelers Class 9 Class 7 Class 9 Semi-tractor trailer Class 9 "Type 6" Class 9 "truck and pup" "...rock haulers,... grain haulers, and oil field equipment trucks. ..." "tandem overload" "combinations" and "single vehicles" "....typically refuse trucks, dump trucks, LCVs, hauling coal and rock." Combination vehicles, "double bottoms" unknown NUMBER OF AXLES 5 5 5 5 5 5 4 or 5*
3* 3 and 5 6 and above 5 and 6
Class 9 (5-axle) vehicles seem to be the most frequently cited overweight vehicles. Officials in Arizona, Arkansas, Delaware, Illinois, Indiana, and Louisiana report that 5axle motor vehicles yield the highest rate of in-state overweight violations. Maryland and Texas officials also identify the 5-axle motor vehicles. Three-axle trucks and six-axle tractor-trailer combinations account for the highest rate of overweight vehicles in Nova Scotia, Canada.
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Question #12 12. What is the ratio of overweight permits you issue to overweight vehicle violations?___________________________________________________ Table 15. Ratio of overweight permits you issue to overweight vehicle violations STATE Alaska Arizona Arkansas California Colorado Delaware Georgia Illinois Indiana Louisiana Maryland Missouri Montana North Dakota Ohio Oklahoma Oregon RATIO 2.18:1 unspecified 11.78% (40,987 overweight permits: 3,478 violations notices being issued.) 3.95% 1.36%; Overweight permits issued ? 15,764, Overweight violations ? 11,561 unknown 60% 2.5% 2% Overweight Permits ? 84,862; Overweight Fines ? 54,116; Approx. 1.6 to 1 unknown "3.22. It is unknown how many violations were written on vehicles not permitted." 5.94% unknown unknown Approximately 0.65 "For calendar year 2004, we documented 24,728 overweight violations. During the same period we issued approximately 154,000 annual and single trip permits. The ratio of violations to permits is 1:6.2." unknown 77.8%; 43,820 permits: 5,663 overweight citations 42.8%; 26,600 to 622 unknown
Tennessee Utah Vermont Wisconsin
It is difficult to interpret these responses. For many the math is clearly incorrect. Most respondents compare permits to citations written. Of course, it seems likely that the number of violations vastly exceeds the number of citations written. In reality "unknown" is probably the only accurate answer in this list of responses.
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Conclusions If anything is clear from these survey results, it is the fact that hard data on overweight vehicles is sorely lacking. The range of estimates for the percentage of vehicles that are overweight ranges from less than 1/2% to a high of 30%. Some perceive a serious problem. Others see no significant problem. No state was able to produce a credible estimate of the amount of damage that might be attributed to overweight vehicles. There is no coherent vision of weight enforcement that permeates the thinking of practitioners. Some enforcement personnel imagine they are weighing nearly every truck. The reality is that only a minority of trucks is likely weighed. Ports-of-entry are not consistently manned and operated. When POEs are closed in the evenings or on weekends the highways are open for overweight violators. Mobile enforcement would appear a potentially useful measure in detecting and deterring overweight vehicles. Yet, the commitment to this strategy varies greatly. Some states' mobile units weigh millions of vehicles yearly. Others weigh just a few thousand. The damage done by overweight vehicles is insidious rather than immediately overt. Roads are long-lived assets. The increment of damage from one overweight vehicle goes unseen. Consequently, it is difficult to stimulate an effective response to counter the damage. Nonetheless, greater attention to the issue is warranted. At the very least, we need better data.
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V. THE CHALLENGE OF OVERWEIGHT VEHICLE ENFORCEMENT While U.S. federal guidelines remain in place, the definition, measurement procedures, assessment, and damage quantification of overweight vehicles vary from state to state. A review of the literature supplements the ESRA survey and demonstrates that the challenges of overweight vehicle enforcement and identification are historic, complex, widespread, and costly. In 1979, the General Accounting Office (GAO) suggested that approximately 15% of all loaded trucks were overweight with respect to allowable axle loads or GVW. The GAO also cited a lack of uniformity among the U.S. states with respect to enforcement, penalties, and permit administration.68 The Federal Highway Administration (FHWA) identified various ways through which truck weight violations were adjudicated.69 The FHWA found that the judicial system did not adequately address the severe social costs associated with overweight vehicle violations. There appeared to be a lack of understanding associated with the implications of such violations. Illegally overloaded trucks were then estimated to cost taxpayers $160 to $670 million per year for pavement costs at the national level. Meanwhile, the illegally operating carriers reaped the benefits of overloading the taxpayer's highways by gaining an unfair advantage over their honest competition through greater profit margins. They also avoided the responsibility of covering the pavement damages they created. Nevertheless, law-abiding carriers and the associations representing truckers supported the stringent enforcement of truck weight laws to eliminate the unfair advantage of illegally operating carriers. By 1987, a published questionnaire distributed to state enforcement agencies revealed that between 10% and 25% of all trucks were overloaded.70 The Transportation Research Board later recommended increased truck weight enforcement, among other things.71 Terrell and Bell reported that majority of state officials that they surveyed perceived truck overloading to be a moderate problem.72 At that that time, it was estimated that 10 - 25% of the trucks were overloaded and that 20%of the vehicles operating on federal-aid highways had axle or gross loads in excess of statutory limits. There were annual estimates of $1 billion impacts on the cost of overloaded vehicles to the federal-aid
68
General Accounting Office. 1979. Excessive Truck Weight: An Expensive Burden We Can No Longer Support. Washington, D.C.: General Accounting Office. 69 United States Federal Highway Administration. 1995. Comprehensive truck size and weight study: Summary Report for Phase I--Synthesis of Truck Size and Weight (TS&W) Studies and Issues. Available from: http://ntl.bts.gov/DOCS/cts.html 70 Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987. 71 Transportation Research Board. 1990. Truck Weight Limits: Issues and Options. Special Report 225. 72 Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987.
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highway system.73 Since 1987, however, the numbers of roads, the volume of overweight truck traffic, and the costs associated with pavement damage have likely increased. Cottrell suggested that, in Virginia, the limited capacity of weigh stations plays a role in the number of trucks running the weigh stations. Avoidance rates at two weigh stations were examined. Eleven to fourteen percent of trucks were found to avoid weigh stations by using bypass routes or waiting until the weigh station closed. In addition, a portable WIM was used to measure the weight of trucks running weigh stations. Of the "run-by" trucks measured, 38% were classified as overweight.74 In 1994, it was found that approximately 25% of the motor vehicles that passed through weigh stations in Connecticut were illegally overweight and fined. Of these overweight vehicles, nearly 10% were identified as commercial solid waste haulers. Enforcement efforts were stepped up by equipping highway patrol units with portable scales.75 South Dakota enacted laws to prevent pavement damage from illegal overweight vehicles. In 1996, the Legislature restricted the maximum weight allowed on axles by ensuring that the weight on the axles fitted with single tires would not surpass the load capacity of the pavement. In 1999, the Legislature upped the graduated penalty schedule as a means to reduce both intentional and unintentional overweight violations.76 Cunagin, Mickler, and Wright examined Florida corridor and bypass enforcement activities through weight station avoidance. They found that the violation rate was significantly reduced through intense enforcement and that weekends were ripe for violations, when POEs were typically closed.77 In 1997, the State of Arizona Office of the Auditor General (OAG) recommended the "increase use of mobile enforcement crews along Arizona's highways." The OAG reported that MVD placed "little emphasis on intrastate enforcement." Motor carrier tax evasion was estimated to account for between $24 million to $45 million in lost potential revenue.78
Terrell, R.L., C.A. Bell, Effects of Permit and Illegal Overloads on Pavements, NCHRP Synthesis 131, Transportation Research Board, 1987. 74 Cottrell, B.H., The Avoidance of Weigh Stations in Virginia by Overweight Trucks, Virginia Transportation Research Council, Charlottesville, VA, 1992. 75 Shanoff, B. 1994. Overweight Trucks Face Hefty Fines. WasteAge. Available from: http://www.wasteage.com/mag/waste_overweight_trucks_face/ 76 South Dakota Department of Transportation. 2002. SDOT Briefing: Truck Weights and Highways. 77 Cunagin, W., W. Mickler, and C. Wright. 1997. "Evasion of weight-enforcement stations by trucks." Transportation Research Record 1570, 181- 190. 78 Norton, D. R, 1997. Performance Audit: Department of Transportation Motor Vehicle Division's Revenue Functions, Report to the Arizona Legislature, Report No. 97-4. Phoenix: State of Arizona Office of the Auditor General. http://www.auditorgen.state.az.us/Reports/State_Agencies/Agencies/Transportation,%20Department%20of /Performance/97-04/97-4.pdf
73
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The challenges of weight inspections and enforcement faced each day by MVDs and Public Safety officials were best documented in a 1999 edition of the Texas Transportation Researcher. It was reported that approximately 320 Texas Department of Public Safety troopers conducted about 85,000 weight inspections each year on more than 200,000 miles of Texas highways. Dan Middleton, manager of Texas Transportation Institute System Monitoring Program, noted that "This equates to one trooper for every 45 million vehicle-miles traveled by truck in the state -- a number far too small to catch every violator.... We need a system to screen trucks in the traffic stream and identify those that have a high likelihood of being overweight... and need to be weighed statically."79 A steady increase in truck traffic, attributed to the North American Free Trade Agreement (NAFTA), results in more than $60 billion of freight -- about 70% of the total dollar value of trucking freight in the U.S. -- crossing the Texas-Mexico border.80 Although truck weights and standards comprise a part of the NAFTA plan, they do not include any provisions to raise U.S. federal or state truck size and weight limits. NAFTA does, however, lay the groundwork for Canada, Mexico, and the USA to devise compatible standards. Canada and Mexico may have longer sizes and heavier limits on their trucks. Rusfolo, et al. conducted an analysis of the weight-mile tax in Oregon to determine whether the tax influenced changes in vehicle weight or configuration that would result in decreased pavement damage. A review of the Oregon Highway User Database showed that a significant portion of mileage for the heaviest vehicles (GVW over 80,000 pounds) was reported incorrectly and was not reliable. The data were not considered conclusive and no changes could be attributed to the weight-mile tax.81 A recent sweep of waste trucks in Pennsylvania yielded 40 citations for overweight vehicles. These constituted about 10% of the waste trucks that were identified by Pennsylvania State Police.82 The Maryland State Highway Administration reports that in Maryland, there are 12 fixed Truck Weigh and Inspection Stations and seven pull-off locations. Mobile enforcement crews serve these pull-off locations. There are 22 roving enforcement teams that patrol Maryland highways. These crews enforce Federal Motor Carrier Safety Regulations and canvass the highways for those who avoid the scales.83 Two new WIM systems increased the number of vehicles weighed in Maryland by 57% in 2003. This amounted to a slight increase in the $8.5 million in fees collected through
79
Middleton, D. 1999. Keeping overweight trucks from getting a-weigh, Texas Transportation Researcher, 35:(3), 1-2. 80 Ibid. 81 Rufolo, Anthony, Lois Bronfman, Eric Kuhner, Effect of Weight-Mile Tax on Road Damage in Oregon, Oregon Department of Transportation Research Group, September 1999. 82 Pennsylvania Department of Environmental Protection. 2002. State Solid Waste Plan. Available from: http://www.dep.state.pa.us/dep/subject/advcoun/solidwst/2003/Draft_Chapter3_Municipal%20Waste.pdf 83 Maryland State Highway Administration, Office of Traffic and Safety, Motor Carrier Division. 2003. 2003 Annual Report: Maryland Motor Carrier Program.
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oversize/overweight permits each year. A review of the data of weight enforcement activities from 1998 to 2003 shows that more vehicles are weighed on fixed scales than on WIMs. However, with the addition of two new WIMs in strategic locations, not only is there a dramatic increase in the number of vehicles weighed on WIMs, but also a difference of nearly 10,000 vehicles weighed between the static and the WIM scales. Additionally, an Automated Hauling Permit System is used for permit issuance. This not only involves a smaller staff to operate, but it also provides a faster turnaround time for permit applications.84 In Maryland, trucks deliver nearly 81% of all manufactured freight. They are vital to the economy because they can "access 92% of the state's communities without special accommodation."85 In North Carolina, in 2005, ".... more than 100 vacancies in the ranks of weight enforcement officers and the patrol's lack of emphasis on catching overweight trucks"86 halved the overweight truck citations in the span of 5 years. Legislators responded by earmarking monies to the North Carolina Highway Patrol to increase the number of weight enforcement officers and improve its activities. Another challenge for law enforcement officers is the presence of large trucks on roads other than highways. Large trucks are already a hot button in some residential communities. In Tucson, Arizona, for example, an increase in pollution, noise, and pavement damage led Rincon Valley residents to petition to limit the size of trucks on the streets to those with a 3/4-ton rear-axle load capacity. While Pima County officials review the policy of imposing a strict weight limit on residential streets, they are unable to enforce it because there are no scales and roving weight enforcement officers on the beat in residential communities in Tucson.87 Other cities across Arizona and the U.S. face similar obstacles as the volume of traffic escalates over the next 50 years and spills from the highways and unto the residential roads. ESRA obtained data on ratios of total overweight permits issued and overweight vehicle violations to heavy truck traffic (see Tables 16 and 17). All data, for the year 2003, were obtained through the DOT/FHWA websites. The permits include the total "number of overweight permits issued by States for non-divisible and divisible single trip load movements, non-divisible and divisible annual (or multiple use) load movements, and for divisible over-width load movements."88 According to the DOT/FHWA, the state weight violations include the total "number of trucks cited or issued civil assessments by the
Maryland State Highway Administration, Office of Traffic and Safety, Motor Carrier Division. 2003. 2003 Annual Report: Maryland Motor Carrier Program. 85 Ibid. 86 Stith, P. 2005. "Troopers ticketing more heavy trucks." The News and Observer. Published 17 August 2005. Available from: < http://newsobserver.com/news/story/2728787p-9166402c.html> 87 Ellis, T. 2004. "Big trucks an issue on residential streets." Arizona Daily Star. Published 5 June 2004. Available from: 88 United States Department of Transportation, Federal Highway Administration. 2005. Freight Management and Operations: Permit Facts and Figures FY 2003. Available from: http://ops.fhwa.dot.gov/freight/sw/permit_report.htm
84
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States for violation of weight laws. Also included are the numbers of trucks that were required to off load or shift their load to be in compliance with the weight laws."89 Table 16: State Permits and Weight Violations, Fiscal Year 2003*
Total Total VMT Permits/ Violations/ Permits/ Violations/ overweight overweight heavy Heavy 1,000 1,000 million million permits vehicle trucks Trucks issued violations (millions) (1,000s) trucks trucks VMT VMT 25,507 17,693 2,575 54.8 9.9 6.9 465.5 322.9 7,058 587 109 5.9 64.8 5.4 1196.3 99.5 83,651 28,457 1,380 31.5 60.6 20.6 2655.6 903.4 38,787 10,597 482 22.1 80.5 22.0 1755.1 479.5 197,750 77,735 6,889 200.3 28.7 11.3 987.3 388.1 15,764 22,077 367 29 43.0 60.2 543.6 761.3 64,615 6,714 535 21.1 120.8 12.5 3062.3 318.2 175,281 372 183 6.5 957.8 2.0 26966.3 57.2 1,578 271 1 0.1 1578.0 271.0 15780.0 2710.0 2,477 76.5 0.0 0.0 0.0 0.0 69,528 51,009 1,094 50.2 63.6 46.6 1385.0 1016.1 2,767 1,248 77 5.2 35.9 16.2 532.1 240.0 61,444 14,429 1,471 56.8 41.8 9.8 1081.8 254.0 133,619 71,584 11,191 177.5 11.9 6.4 752.8 403.3 207,609 10,937 4,552 95.3 45.6 2.4 2178.5 114.8 30,544 16,407 976 45.2 31.3 16.8 675.8 363.0 43,386 20,104 1,404 52.8 30.9 14.3 821.7 380.8 86,380 7,020 1,025 40.3 84.3 6.8 2143.4 174.2 85,487 62,811 693 25.5 123.4 90.6 3352.4 2463.2 19,373 1,901 231 11 83.9 8.2 1761.2 172.8 145,160 21,827 290 15.8 500.6 75.3 9187.3 1381.5 69,939 5,715 898 29.8 77.9 6.4 2346.9 191.8 123,492 5,503 2,528 80.3 48.8 2.2 1537.9 68.5 24,180 3,902 2,536 68.4 9.5 1.5 353.5 57.0 137,057 24,969 675 13.3 203.0 37.0 10305.0 1877.4 43,997 22,006 2,880 68.6 15.3 7.6 641.4 320.8 13,585 8,203 154 17.4 88.2 53.3 780.7 471.4 54,186 22,925 2,852 54.3 19.0 8.0 997.9 422.2 18,514 1,007 263 10.1 70.4 3.8 1833.1 99.7 2,160 314 12.6 6.9 171.4 9,592 2,826 2,807 75.9 3.4 1.0 126.4 37.2 17,881 1,329 323 13.1 55.4 4.1 1365.0 101.5 193,970 9,551 1,767 79.7 109.8 5.4 2433.8 119.8 72,493 32,999 4,327 103.7 16.8 7.6 699.1 318.2 49,794 17,759 35 35.2 1422.7 507.4 1414.6 504.5
State Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware DC Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota
United States Department of Transportation, Federal Highway Administration.. 2005. State Information on Citation and Civil Assessments Issued for Overweight Violations: State Weight Violation Facts and Figures FY 2003. Available from: http://ops.fhwa.dot.gov/freight/sw/violation_report.htm, and U.S. Census Bureau, Vehicle Inventory and Use Survey, http://www.census.gov/svsd/www/02vehinv.html.
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State Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming Total
Total Total VMT Permits/ Violations/ Permits/ Violations/ overweight overweight heavy Heavy 1,000 1,000 million million permits vehicle trucks Trucks issued violations (millions) (1,000s) trucks trucks VMT VMT 120,775 24,808 4,609 118.5 26.2 5.4 1019.2 209.4 37,541 1,847 19,428 233.4 1.9 0.1 160.8 7.9 132,381 22,179 615 16 215.3 36.1 8273.8 1386.2 112,140 1,453 737 44 152.2 2.0 2548.6 33.0 15,328 238 91 3.7 168.4 2.6 4142.7 64.3 54,712 12,170 1,516 31 36.1 8.0 1764.9 392.6 43,443 6,374 646 22.6 67.2 9.9 1922.3 282.0 104,081 8,558 2,963 59.1 35.1 2.9 1761.1 144.8 193,320 71,745 7,616 164 25.4 9.4 1178.8 437.5 20,286 11,320 1,489 25.2 13.6 7.6 805.0 449.2 26,785 1,256 260 8.4 103.0 4.8 3188.7 149.5 79,954 136,120 1,704 44.6 46.9 79.9 1792.7 3052.0 139,369 17,944 1, 3 3 3 41.5 104.6 13.5 3358.3 432.4 71,036 3,344 699 21.7 101.6 4.8 3273.5 154.1 21,109 8,175 2,653 61.3 8.0 3.1 344.4 133.4 48,221 2,275 279 11 172.8 8.2 4383.7 206.8 3,544,449 934,440 106,999 2,592 33.1 8.7 1367.6 360.5
*Sources: DOT/FHWA, 2005; VMT = vehicle miles of travel and United States Census Bureau, http://www.census.gov/svsd/www/02vehinv.html We find that Arizona has a higher ratio of permits and violations per heavy truck vehiclemile of travel (VMT) and per registered heavy truck compared to the average of all the states. This supports the premise that overweight trucks are more prevalent in Arizona than most other states. However, a nationwide comparison may not be as relevant as a neighboring state comparison. Interstate trucks traveling through Arizona also travel in the neighboring states. A vehicle that is overweight in one state is likely overweight when it enters a neighboring state. Table 17 shows overweight permits and violations for Arizona and its neighboring states.
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Table 17: Arizona & Neighboring State Permits & Weight Violations, FY 2003
Total Total VMT overweight overweight heavy Heavy Permits/ Violations/ Permits/ Violations/ 1,000 1,000 million million permits vehicle trucks Trucks issued violations (millions) (1,000s) trucks trucks VMT VMT 83,651 28,457 1,380 31.5 60.6 20.6 2,655.6 903.4 197,750 77,735 6,889 200.3 28.7 11.3 987.3 388.1 15,764 22,077 367 29.0 42.9 60.1 543.6 761.3 18,514 1,007 263 10.1 70.4 3.8 1,833.1 99.7 17,881 1,329 323 13.1 55.4 4.1 1,365.0 101.5 20,286 11,320 1,489 25.2 13.6 7.6 805.0 449.2 353,846.0 141,925 10,711 309.2 33.0 13.3 1,144.4 459.0
State Arizona California Colorado Nevada New Mexico Utah Total
Table 17 indicates that Arizona is selling more overweight permits per heavy truck VMT and per registered heavy truck than most of its neighboring states. This evidence implies that Arizona is relatively aggressive in its efforts to induce overweight vehicles to purchase permits. In terms of overweight violations, Arizona issues more citations than most of its neighboring states. This evidence may suggest that Arizona is also relatively aggressive in catching violators at its state and national borders. These data may suggest that Arizona extracts greater revenues from overweight trucks and catches more trucks that evade the permit fees than neighboring states are. Further studies are needed to determine if these data can be correlated with interstate trucks moving across state lines since many states have passed weight exemptions for local industries. Hence a lack of enforcement may be a matter of state law90. According to FHWA estimates, urban areas and the Interstate Highway System will account for the bulk of truck traffic growth anticipated in Arizona over the next 15 years (see Appendix A), particularly along I-10.91 Clearly, continuous maintenance of the state's highway infrastructure is a necessity. Carey estimates that vehicles in the heaviest weight class, i.e., those registered at 75,000 lbs. and over, underpay state taxes and fees by the widest margin, irrespective of the highway cost allocation model employed.92 Using Carey's simplified model, the Arizona Department of Transportation's Financial Management Section estimates that these vehicles impose approximately $35 million per year in uncompensated pavement wear.93 This implies there is a substantial amount of evasion of overweight vehicle regulations. Such challenges lead Strathman and Theisen to support weight violation penalties that "...effectively relate the economic incentives to overload and the consequential damage to roadways."94
Anonymous TRB reviewer, October 2005. Comprehensive Truck Size and Weight Study, Final Report. Batelle Team, Federal Highway Administration, US Department of Transportation, August 2000. 92 Carey, J. 2001. Implementation of the Simplified Arizona Highway Cost Allocation Study Model. FHWAAZ-01-477(3). Phoenix, Arizona: Arizona Department of Transportation. 93 Arizona Department of Transportation, Financial Management Section, internal report, June 21, 2005. 94 Strathman, J. G. and G. Theisen. 2002. Weight Enforcement and Evasion: Oregon Case Study. FHWAOR-DF-02-12. Salem, Oregon: Oregon Department of Transportation.
91
90
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VI. PAVEMENT DAMAGE ESTIMATION Initially, ESRA pored over WIM data collected over several years across different Arizona ports. This data was to be used to try to quantify the pavement damages associated with overweight